I have one of each. The east german Mak is a bit bigger and heavier, and mine has a really nice trigger, both da and sa. It is built like a tank, and has been completely reliable through hundreds of rounds, and shows no wear whatever.
The PA-63 is a skosh longer in the nose, lighter because of the alloy frame, and flatter than the Mak. It has a fairly stiff da pull, but the sa pull is comparable to the Mak, which is pretty nice, although I can't check the actual weight. The grip doesn't fit as well as the Mak, and the curved backstrap doesn't feel quite right to me. Recoil is snappish, more so than the Mak, probably because of the weight. Mine is blue, but they also come as a two-tone, and generally run for $20-$30 less than a Mak. It's well made, although the machine work on the frame is a bit rougher than the Mak. The slide displays comparable quality. It also has digested hundreds of rounds with no problems or malfunctions, and shows no ill efects.
Both have the same takedown system, i.e. pull the trigger guard down, pull the slide back, up, and off, just like the Walther PP series.
I can't really say which I prefer. I bought the Mak because I was very impressed with the quality for the price. East german Makarovs are some of the best built examples of the breed, and generally cost a bit more than others. (Bulgarian, Russian) I bought the PA-63 as a poor man's Walther PP, and because the wholesale price was under $100, which made for a take-home price of under $150 here in the PRK.
The Makarov is better built (at least cosmetically) and a nicer shooter (trigger, grip, recoil). The PA-63 is cheaper, and IMO looks neater (the James Bond factor). Concealability as well as accuracy are interchangable, near as I can tell. Long term carry probably favors the PA-63, but only because it's lighter, and that's really of no consequense when actually comparing the weights. They're both sufficiently light.
I wish the PA-63 had a straight backstrap. FEG also makes the SMC .380 (it comes in 9 x 18 too) and another, slighly smaller gun (who's designation I can't remember) that have the straight backstrap, and a slightly different appearance, so that option realistically exists, although I don't offhand know prices.
I think PA-63's are still going for $89 blued and delicately used, $99-$109 in tutone NIB. I've read on TFL that Bulgarian Makarov's are going for as little as $109. All prices wholesale.
PA-63's are less common then Maks at dealers, I guess because Maks probably sell a little better. I would suggest handling both to see which you prefer, as to all intents and purposes they're darn near interchangable.
I hope this clarifies your question somewhat. My personal solution is to buy both, as I think everybody needs more guns.