They're all the same, the MK5 has a couple of extra features, but the MK2 will still play a record just as well.
They are very expensive these days since they got discontinued.
The main reason for sticking with 1200's (apart from the obvious durability) was not due to the features (they dont have any) but because most club setups would have them. So if you practiced at home on a different set, it would take some adjusting to in a club environment.
Nowadays most clubs do not have 1200s as the main setup so having those turntables specifically is not longer a necessity imho.
If I had to buy something now I would choose something I would make the most of, not something I felt had the biggest following - You wont need the best of the best if all you are doing is playing a record and mixing, but you might need something with more torque if you plan on scratching / juggling etc - and if you are using it for turntablism, there are decks out there with more torque than the 3.5lbs that a 1200 has
