Not sure which pirates have done both to give you a fair assessment. I've done IMDE which was absolutely amazing! You are treated like kings and queens and nothing is forgotten.
Where do you live? Not all the regional airports fly there (and Frankfurt Hahn is MILES away). Once you arrive at Frankfurt Airport there's a train to take you into town that's easy enough if you don't want to pay for a cab (cabs are naturally quite expensive).
The pirates have stayed at both the youth hostel and an Ibis locally en masse. The Ibis we stayed at was the Ibis Frankfurt Centrum and you get what you paid for really. Clean, very small rooms but also not very expensive either, so if you can put up with the travelodge ethos, it's fine. This hotel is right on the turn point of the run route so it's not very far away from transition and it was an easy enough walk home afterwards. There are closer though.
The race - the swim is in a lake that you are bussed out to (it's all very well organised though by the race though and is free of charge for the buses) but beware that IMDE has has a few non-wetsuit swims now as it gets quite warm there.
The bike leg is a double looper with three 'named' hills but none are going to kill you and the atmosphere on Heartbreak Hill is amazing.
The run leg takes you on four loops along the river so you get to see your fellow athletes loads, the support here is amazing. It's completely flat apart from the bridges which start to look like mountains in the end!
There is a cobbled section on the bike and cobbles on the run.
The last thing of note - IMDE has a shorter cut off, not the standard 17 hours and it's either 16 or 15 hours. If you think that you are a back marker, think carefully about whether you need that time at the end or not.