The biggest noticeable issues with the Trumpeter kit are the misshapen lower rear hull (to accomodate the motor) and the sprockets. The rear hull is easily fixed with a little cutting and replacing of the lower plate with sheet styrene. The sprockets can be replaced by Esci parts, left off entirely, or just bent and mangled. If you do have an Esci donor kit, it wouldn't hurt to replace those tow hooks as well.
If you're wondering why someone would have a dozen "donor" lying kits about, there was a time when the cheapest/best way to obtain proper T-62 wheels was to make them from the Esci wheels.
As for the Skif kit, IMHO, it doesn't even make for a good wreck. The wheels are horrendous and the lack of undercutting on the turret race armor make it far too toylike. Trumpeter kits can be found for $5.00, and with the engine from one of their Chinese howitzer kits, you can get a lot of bang for the buck at far less than Tamiya prices.