Can’t say much about planes (my highest is the Fw 190-D9) or ships (light cruiser Emden or so) because I’m here for the tanks, although puttering around on a ship sometimes is fun, but I haven’t done either in months.
Tanks in PvE (Assault Ground Arcade), then. My favourite preset has the two Tiger I plus the four Panthers, so 5.7 to 6.0. I like playing it enough that the crews for four of them (Tigers and Panther A/G) are ace now. (No buying, just points.) Next in ranking would be my Panzer IV H (the first ace crew I had) and the VK 30.02, although both have crap target scopes, and the VK’s turret rotation is rather slow.
I was looking forward to playing the higher brackets but that was so far a bit of a disappointment. Worst point here is probably the ammo shuffling from the main storage to the ready rack in the turret bustle, or that the reload time in a Leopard 2A4 goes toward infinity when the ready rack is empty, I think even the IS-2s are suffering laughing fits.
Also, Sinai (not my favourite map to begin with) is in my opinion somewhere between not worth playing and unplayable for the 8.3+ bracket.