I've got some hours on the BE55 and it flies very nicely. Maybe one of the best aircraft I've flown.
I've seen the most recent BE58 at the EBACE and I was surprised.
Another point:
Not sure about the Seneca (I think no) but the old version of the Baron is pressurized!
It is also, IMHO, more strong and better built.
I'd go for the Baron.