The gun on the AMX 50 100 is:
Damage 180-300 HP
Penetration 128-213 mm
...but it shoots 7.4 rounds per minute (i..e slow reload on the clip)
The American Tier 8 with an autoloader is the T69 - which is a medium. It's gun is:
Damage 113-188 HP
Penetration 131-219 mm
...and it shoots 12.9 rounds per minute.
So with the American tank you have higher penetration with less damage - but you can shoot more often. With the Black Prince, having penetration is important (although those penn numbers are pretty much the same)
Both tanks are pretty squishy and need to be played more as a medium than a "slug it out" heavy like a T34 or Black Prince.
Graham (Dookie Chunkz) has the French Heavy line all the way to Tier X
I have the American equivalents to Tier X as well (on both American Heavy lines).
If you catch us in Team Speak we can start a training room and pull whatever tanks you want to check out and compare.