Friuls and SpadeAce are both easy to assemble, especially when the links are the size these will be.
I've taken a liking to SpadeAce lately, but the Friuls are also very nice. Both are about $30 from Lucky Model (or Hobby Easy, I always forget which) and shipping is very reasonable.
Friul's wire is a little soft for my liking, SpadeAce's stiffer but still cuts and files easy. I sometimes use steel piano wire from the hardware store but it's hard steel and more difficult to clean up the cut. Brass wire works also, easy to find too. I always try to cut the wire short enough that the end is inside the link, not protruding, and then fix it in place with cryo glue.
Also, all the SpadeAce tracks I've used so far have had the holes all the way through the link, and Friuls do not, having the appropriate bolt,nut,cap, whatever, on one end. Works great if the tracks are not "directional" like a T-34, enabling you to hide the "open" side of the links on the inside of the model.
My take on MK: tedious, because there are two pins for each link, and you have to be gentle when painting and weathering because they're plastic. Trumpeter also makes some plastic MK-type T-55 tracks, never used them though.