I'm f2p player so premium account does not happen often, so didn't realize this before. I'm grinding ToTT and noticed that there is huge difference with exp received with premium account. You may think that premium account provides 50% bonus, but that's not true.
Typical grind set: +100% exp, bonus for the crew (that's irrevelat), won battle with poor score (but this is irrevelant too).
Without premium: 446 base exp. +100% personal reserve, +100% for first win. 1338 together.
With premium: 669 exp, 2007 together. But can apply premium multiplier x3 for base exp, which makes 4014. It's three times more, or +200% exp.
But that is not the end. For other wins than first and without personal reserves it would be:
Without premium: 446 base exp.
With premium: 669 exp + 2007 bonus = 2676
That's six times more or +500% exp. That's very much.