It has made a huge difference. Loss rates and survivability of western hardware in Ukraine are vastly better than the Soviet equipment, and the Ukrainians will say as much.

There are caveats, like: a tank that hits a mine is going to be disabled one way or another, and a disabled tank won't survive too long if it's anywhere near the front.

The problem isn't the quantity of equipment, it's the quantity of munitions. For example, Ukraine has only 30 or so HIMARS units but that's more than enough to fully consume every GMLRS munition we can provide them.