Help me choosing the race before A-Race

Hi I want to finish my first full IM next year in Hamburg. Before I want to make another 70.3 either Iroman 70.3 Graz or Challenge St. Pölten.

my thoughts:

St. Pölten:
same start time 7am like IM Hamburg (Graz: 9am)

much more altitude
different organiser
swim in two lakes

If I would not race IM Hamburg I would choose St. Pölten because the race looks more interesting and I would like to race at a different organiser (raced one IM 70.3). But I am wondering if it is a problem that the bike course is much more demanding in terms of altitude then IM Hamburg and if it is good to race at a different organiser 4 weeks before A-race.

THANK YOU for your thoughts!