I have flown CSA on the european flights, and I must say, while their service is ok, I would opt for LH. LH has a better on time record with me, an the interiors of their aircraft are nicer. Their cabin service is a toss-up...depends on the crew. However, you will probably get more food on a CSA flight than you would on LH.
I have never flown on their long haul services...I have heard lots of negative things about the reliability of those two poor A310s, but I have heard the service is better on those flights than on their european ones (which is ok, anyway). Whatever you do, if you get on a CSA 737, watch out for the seats that don't lock upright...I always seem to get those, and its no fun. Either way, hope you have a great trip!