The Hyatt not only offers the reliability of a 4 Star hotel chain but it is a beautiful property right on the Intercoastal Water Way. You can catch the water taxi at their marina. You can watch sunset from the rotating lounge atop of their tower building - what a way to start a vacation watching other ship's pull out the night before you cruise. You will pay for this experience unless you are lucky with bidding or have a special price, but it can be worth the extra expense. The Renaissance is just the newest hi-rise hotel on the corner closest to the pier.
Stayed at Pierr66 2 years ago and loved it. Right on the water, views of cruise ships in port, accessible water taxi. We had a room that opened up to a canal lined with beautiful yachts. Don't know much about other hotel.
Have stayed at both (Hyatt July 2001, renaissance July 2002) and think that it just comes down to personal opinion.
The Hyatt is a lot more "resorty":
- big pool and external gardens,
- well equiped fitness centre,
- several restaurants/bars/coffee shop etc,
- right on the inter-coastal waterway (great views and can catch water taxis near by).
- rooms are nice and large (we had a ground level room on the inter-coastal waterway - nice view of large luxury yachts moored right next to our patio!).
The Renaissance in a bit more of a business hotel:
- very modern and clean and bright,
- rooms are large and very modern and bright, beds are SOOOO comfortable!
- fitness centre is small and fairly basic (ok, but not much room and not a HUGE choice of different cardio machines),
- pool is small and located right next to the main road (with a wall in between),
- restaurant is nice (only tried breakfast there) - food is very good, but service was slow.
Both are well located for pier, restaurants and shops. The Rnaissance is normally a bit cheaper than the Hyatt.
I probably prefer the Renaissance to the Hyatt, but that has something to do with us flying in from the UK: am not normally too bothered about things being "resorty" when I arrive (just need a quick snack and a comfortable bed...). Then, the next day, I just go to the gym, eat breakfast, then get all hyper about the cruise :-)
This year we are doing things a bit different, though - we are arriving an extra day earlier (because we are travelling on airmiles, they didn't have availability the day before the cruise). I have booked the Embassy Suites through Hotwire: have only heard very positive things about it, it includes free breakfast and cocktails each day and only cost about $56 a night. This seemed like a bargain too good to miss...
Good luck, whatever you decide. Hope my post helps.