Personally, I think the "lower level" teams tend to be the most interesting and entertaining, but at the same time I do like watching the athletic, young competitive teams. I would like a mix of both, but preferably less 'über competitive' teams.
For example Dave and Cherie last season were the 'Married Clowns' and I thought they had a nice story and they were very entertaining. BUT all the other teams were so über competitive that they didn't really get a chance to go far.
Most of you might know Lucy and Emilia (Italian Sisters/Teachers) from the current The Amazing Race Australia 2
They aren't cut-throat competitive, they aren't the most athletic team, they aren't the strongest, yet they are the fan favourites (it's their great attitude that keeps them in the race)
They have an interesting story - their mother had cancer and she encouraged them to do the race together, and they are such a great team to watch!
Whenever the cast is revealed, it's easy to tell whether it's a good cast
1. Every team has an interesting story or motivation to run the race
2. The cast age range (e.g. TAR16 - youngest contestant was 20 and the oldest was 71)
3. Diversity (professions, nationalities, relationships etc)
I wish WRP would cast some MORE "low level" teams, and from our TAR21 Spoilers, it looks like they have improved on casting, we'll have to wait and see