Yes, the 2.1 is the more desirable, the 2.5 has a hydraulic clutch making it much lighter and the performance is a bit better but that is where the advantages end, its even more difficult to work on that the 2.1 due to the fact that the engine only just fits in, its also more complicated, the spares are expensive and very difficult to get, so unless tyou are only going to do a very low mileage I would give it a miss.
The only problem the 2.1s suffer is the head gasket, on my cars its usually been at about 150k, they are not easy to change but once done you can be pretty confident that you will get another 150k without any major problems. Otherwise the engines are pretty bombproof, I have had clutches last in excess of 250k and I had one crankshaft pulley fail but again that was at about 250k.
Peter