I was curious the other day while looking at these two razors if they are the same head or not. They look so similar that I had to take some pics to compare.
The ER is on the left and the Gem is on the right. You can see pretty clearly that the Gem has a wider outer flange and taller teeth. The top cap is pretty much the same in this angle.
From these angles you can see that the Gem has more blade exposure. You can also see the differences in the teeth.
Angles are pretty much the same on the handle and head.
Here you get a good picture of the blade exposure. The Gem has quite a bit more which has the potential to make it more aggressive. You can also see the differences in the front flanges.
Overall these are both incredible razors. It would be hard to tell which one is better. Both are very well balanced. If I had to pick one I’d choose the Gem due to the wider more rounded flange and taller teeth. That’s just me though.