If you are a first time renter then you should lean towards a shorter RV with length of about 25-30 feet, the shorter the RV the easier it will be to drive and maneuver.
If you plan to spend most of your time exploring and outdoors then you should prefer shorter RV. If you plan to stay at multiple RV Parks and visit various national parks then a shorter RV will be easier to drive.
If gas price is a factor in your budget then you should rent shorter RV.
On the other hand if you are heading straight towards Florida and plan to spend few weeks in one spot then perhaps a longer RV may be more suitable for your needs.
You can also refer to a traveler’s feedback on this Tripadvisor thread:
Yet another international RV renter provides similar feedback on difficulty in driving a 32 feet RV: