With user-made content such as the new STA mod, I believe Steel Fury has many more playable vehicles than Steel Beasts, with more being added from time to time eg Sherman variants. Not all have 3d interiors but they are good, for those that do, complete with animated crewmen eg you can see your loader put a round in the breech when reloading (user-made Tiger I driver's position and T-34/76 turret interior illustrated).
Many of SF's playable vehicles are illustrated here:
http://stasf2008.ephpbb.com/t22-available-units-in-sta-modMarko also mentions Steel Armour - Blaze of War (SABOW) which is a different sim again, a rather strange mix of a tanksim inside the shell of a tactical wargame with a rather complex interface. I don't know if there's a demo for SABOW but it's available very cheaply (in the UK anyway). It has just two playable vehicles stock, the M60A3 and the T-62. It has excellent visuals and for the playable tanks, very good animated interiors:
Edit - Steel Fury - Kharkov 1942 demo is here:
http://www.fileplanet.com/181768/180000/fileinfo/Steel-Fury---Kharkov-1942---DemoIf giving this a try I would recommend you refer to the list I made here of the (main) keyboard commands, which is also where you will find links to the STA mod if you decide to proceed:
http://stasf2008.ephpbb.com/t6-steel-tank-add-on-steel-furyFileplanet also has a demo of Iron Warriors - T-72 Tank Command aka Balkans on Fire:
http://www.fileplanet.com/161763/160000/fileinfo/Iron-Warriors:-T72-Tank-Command-Demo
It's also worth checking out gameplay videos on Youtube, in case you haven't, already, like these:
https://www.youtube.com/watch?v=Ev0sdpCv1X0&feature=youtu.behttps://www.youtube.com/watch?v=PsLfwtR1TVYhttps://www.youtube.com/watch?v=N3QXvixI18chttps://www.youtube.com/watch?v=D0fRswMc-dMhttps://www.youtube.com/watch?v=nhEmEHwQ6wo