Well, I've learned to use the T110E5, and generally surviving a battle = getting cash, getting blown up = losing cash, mostly to resupply ammo.
I also have an M8A1 and a couple other lower Tier vehicles, and I must say it's a bit more fun in the low Tiers sometimes, because it ain't possible to blow stuff up as quickly in the E5, even though I have a rammer, vents and BiA, so it probably takes just a bit more than 8 seconds to reload.
Anyone else get the impression that high Tiers are a bit more static (and I'm not even counting Arty Parties)?
On the other hand the E5 didn't meet an opponent immune to its fire yet, and the M8A1 sometimes struggles, so the lower Tiers also have their problems.
As for US heavies vs mediums, the E5 has better armor and a slightly greater punch, while the Patton III reaches much higher speeds and has a quicker reload. All other differences are rather small, since the T110E5 is what an MBT would be if an MBT evolved from a heavy tank, and not from a medium.