If you are going for a soviet vehicle, go for an OT. The Czech & Polish vehicles tend to be better built than the general Soviet stuff.
Between the BMP and Abbott, the Abbott would win out for me. The FV43x series are very easy to maintain and keep running. Also, the automatic gearbox makes it really easy to drive. Make sure you get a good hull as the suspension bushes go and then it gets very expensive, very quickly.
If I were you, I'd also consider a CVR(T). It's lightweight which makes it reasonably easy to work on. It'll fit in an ISO shipping container to get it home, meaning you can spend more on the vehicle and spares. There is plenty of support and spares for it, and something like a Sabre or Scorpion has a good tank-like look about it. The gearbox is like a motorbike.
You can actually fit two CVR(T)s into a normal ISO container with a bit of wiggling, so there's space for spares if you pack it well. If you need to transport it long distances to shows etc. then it'll fit on a normal car recovery vehicle.
If I could fit in one, I'd have it in a heartbeat. Unfortunately they don't come in my size :banghead: