In essence there are three different types:
1. Beogram 4000 - (or 4002/4004/6000) These are the best made decks
and I think they are the best looking - not remote control unless you
get a 4004 and 2400 Beomaster but you have to get up to clean the
record anyway! Very easy to take apart and the later 4002 and 4004 are
not too difficult to service. - My choice - the later 4004 as it is the
one most likely to work!
2. Beogram 8000/8002. Less well made but should have better
performance (but from experience possibly not.) A number of service
issues - difficult to take apart but Dillen now makes the tacho disc so
early 8000s are not the write offs they used to be. The 6002 is not the
same - more like a 4002 but less well made.These do offer datalink and the 8000 offered a brush to clean the stylus automatically - most people remove this the first time they see it in operation! 
3. Beogram 3000/5500/4500/7000 etc. These are all exactly the same
and are lightweight. Pretty reliable but lots of cheap plastic in the
construction. They do offer full datalink.
As far as cartridges are cooncerned, this is the one area where
things have got better. Soundsmith cartridges offer modern sound at a
price and Axel can retip any sort of B&O cartridge.
So to summarise, as far as Tangential tracking decks are concerned:
Best sounding - Beogram 4000 - but not that easy to get working
Most reliable - Beogram 5500 etc - Remote control but not as good a sound.
Best design - that is your call - I think the 4000 but you may think different.
The advantage of the 8000/8002 is that if you get a Soundsmith cartridge, you cannot see it!