done IMA and IMCH and bike leg on relay at Roth
very little to choose between A and CH - both lovely settings, great swims, superb bike legs, flat runs around the cities. A I would suggest is slightly easier bike course to CH. Zurich is however easier to get to than Klagenfurt
Roth is iconic but it has a split transition which can be a pain - the bike leg is very quick and has the Solarberg climb which is like a TdF climb with massive crowds cheering you on. CH has something similar at Heartbreak Hill but not so crowded.
Seen Frankfurt but not competed - and split transition again and a bigger risk of a non-wetsuit swim as the gravel pit gets very warm
heard good things about Barca but not done it so no comment
for me - it's a tough call between A and CH