The regular E4 has an MTK 6582, right? That is an upgrade from the Y300 for sure, but it's still pretty weak, I would not recommend it. The 4 Cortex-A7 cores aren't that bad, it'S enough for most tasks, but the Mali 400 MP2 is really old and weak. If you don't play on the phone I think it would be fine, but this SoC is so old I wouldn't buy any phone with it
I have an Elephone G2, which has the same SoC (well, the "M" version which is a bit underclocked) with the same amount of RAM, and it's pretty fast, had no performance issues so far. The only problem is that the E4g is running 4.4, which doesn't support 64 bit AFAIK, so it might be a bit slower.
I'm interested in when will these topics go extinct completely. There is not much space to improve the custom roms, the newer Android versions wont be running on the phone. It's just a matter of time for everyone to find a replacement for it.
As for myself, I've been working on replacing it for a long time, but it finally seems like it will happen.