Diameter is decided at purchase; everything else is tuning
Of the eight tools here, four are rated for 7 in. or 9 in. wheels and four top out at 4-1/2 in. or 5 in. Nothing in the published specifications for the smaller tools offers a larger-wheel configuration: the rated diameter is set when you buy. DeWalt’s D28499X changes between the two configurations with one keyless adjustable guard. Metabo HPT’s G23SCY2 includes two tool-less guards, one for each size. Makita’s GA7021 lists 7 in. with no 9 in. option, and Milwaukee’s 2785-20 lists both.
So the first question is not how many amps you need. Amperage only usefully compares tools inside the same diameter class.
Read RPM inside one wheel size, never across two
Manufacturers publish different speeds for tools rated for different wheel diameters, so the 6,000 RPM on the D28499X and the DWE402’s 11,000 RPM are figures for different wheels rather than a 45 percent deficit.
Inside the large class, the spread is narrow. Makita’s GA7021 publishes 6,600 RPM. Milwaukee lists 6,600 RPM for the 2785-20 but does not label it no-load, noting higher speeds under load. The D28499X and the G23SCY2 both publish 6,000 RPM. That is a 600 RPM range, roughly 10 percent, across four tools.
DeWalt’s DCG413B publishes no no-load speed at all — the only tool here without one — so if you want to set it against the DWE402 on paper, DeWalt gives you nothing to set it against.
Amperage comparisons only work in matching units
Corded ratings here run 6 A (GA4530), 11 A (DWE402), 13 A (GWS13-50) and 15 A on all three corded large grinders. The D28499X adds 5.3 max HP — useful against other DeWalt listings, not against Makita or Metabo HPT, neither of which publishes one.
Cordless figures are not in the same currency. DeWalt rates the DCG413B at 20V MAX (18V nominal) and 850 max watts out. That does not convert to amps, so you can rank the corded tools against each other on published numbers and you cannot rank a cordless tool against them except on the maker’s word.
Within the corded set, the gap that matters most is at the bottom. The 6 A GA4530 draws under half what the 13 A Bosch does and well under half the 15 A tools.
Corded and cordless are different purchases at this size
One tool breaks the pattern that large grinders are corded: Milwaukee’s 2785-20, rated for 7 in. and 9 in. wheels on the M18 platform, which removes cord management from work like rebar cutting. It is sold tool-only, and Milwaukee’s page points at the M18 REDLITHIUM HIGH OUTPUT HD12.0 pack. One consequence follows: runtime is unstated, because it depends on the pack you buy.
Neither cordless tool here publishes a runtime at all. The cost is the cord: a 15 A grinder is a 15 A load on whatever cord reaches the work, which is a separate decision with its own numbers. The corded-versus-battery trade shows up across tool classes.
What each manufacturer publishes about bind-up
This is where the published record is most uneven, and the pattern is worth having before you shop by disc size.
Bosch’s GWS13-50 publishes an integrated acceleration sensor stated to mitigate inadvertent recoil, along with restart protection and overload protection.
Then the large tools. Milwaukee publishes a dual-action trigger and REDLINK PLUS protection against overload, overheating and over-discharge, but names no kickback brake. Metabo HPT publishes a Lock-Off/On trigger and User Vibration Protection — rubber handle dampers plus an anti-vibration side handle — and states no kickback brake. Makita is the most explicit of any maker here: the GA7021 and GA4530 spec sheets both list Bind-Up Control: No and Electric Brake: No, and both tools use lock-on switches with no lock-off.
Read across all four tools rated for 7 in. or 9 in. wheels and none of them publishes a bind-up or kickback brake feature, while two 4-1/2 in. tools and one 5 in. tool do. If named electronic safeguards are what you are shopping for, that is not where the large-diameter class in this group currently sits.
Weight and length, compared inside a class
Weight only compares within a diameter class, since a 9 in. tool is heavier by design. Among the large tools, two publish a figure: the GA7021 at 12.2 lb net and the G23SCY2 at 13.9 lb. The D28499X and the 2785-20 publish no absolute weight, so for two of the four large tools there is no number to plan a shift of vertical or overhead grinding around.
Among the smaller tools, the published figures are 3-3/4 lb bare for the DCG413B, 4 lb net for the GA4530 and 5.3 lb for the GWS13-50. The DWE402 publishes no weight.
The same four tools that publish a spindle thread also publish an overall length: 10-1/2 in. for the GA4530, 12.3 in. for the Bosch, 18-5/8 in. for the GA7021, and 19.7 in. for the G23SCY2, which also lists a 3.25 in. head height.
The documentation gap that costs you a wheel order
Four of the eight publish a spindle thread, and all four publish the same one: 5/8 in.-11 UNC on the GA7021, GA4530 and GWS13-50, and 5/8 in. x 11 UNC on the G23SCY2. DeWalt publishes none for the DWE402, D28499X or DCG413B, and Milwaukee publishes none for the 2785-20. For concrete work that is a live issue, because diamond cup wheels mount on that thread — and two of the four tools rated for 7 in. and 9 in. wheels give you nothing to check a cup wheel against. It is not a reason to rule those tools out, but it is a gap to close with the seller rather than assume.
When the small tool is genuinely enough
A 4-1/2 in. tool is the right buy when the work is occasional: deburring, rust removal, finish grinding, light cutting. The GA4530’s 6 A and 4 lb net describe exactly that tool — the lowest published draw here, short at 10-1/2 in., with no electronic safeguards published. The DWE402 sits a step up at 11 A and carries the fullest published safeguard set of any corded tool here, which is the version of a small grinder that makes sense if it will see weld cleanup rather than a few minutes of rust removal.
It stops being enough once the job is defined by how much steel or concrete has to come off.
The in-between case is Bosch’s GWS13-50 at 13 A — more current and a larger wheel than either 4-1/2 in. corded tool here, and still unable to run 7-9 in. wheels. If the work is mostly small with occasional heavier passes, that is the shape of the compromise. If it is genuinely split, the specifications point to two tools rather than one.
The maintenance and warranty specs that differ
A few durability details are published and worth reading because they are not the same across the group. The DWE402 has a dust ejection system that expels debris entering the motor housing. The GA4530 and GA7021 both use labyrinth construction, with zig-zag varnish sealing the GA4530’s motor and armature.
On warranty, all three DeWalt tools state a 3-year limited warranty with 1 year free service and a 90-day satisfaction guarantee. Makita’s GA7021 shows a one-year badge with no further terms, and Metabo HPT covers the G23SCY2 under a one-year tool warranty with no further terms published. No warranty terms appear in the specifications retrieved for the Bosch GWS13-50, the Makita GA4530 or the Milwaukee 2785-20.
