There's no single best grass for Southwest Florida. The right one depends on how much sun the yard gets, whether it's irrigated, how close it is to salt water, and how much mowing and care you want to do.
Floratam St. Augustine
The most common lawn here. Coarse, dark green and quick to fill in, but it needs full sun. In shade under oaks or between houses it thins out. Watch for chinch bugs in hot, dry weather.
Zoysia
Dense and fine-textured, with better shade and salt tolerance than Floratam. It grows slowly, so it recovers slowly too, and it needs a sharp mower.
Bahia
A tough, low-input grass for big or unirrigated areas. It browns and goes dormant in drought and recovers with rain. It doesn't handle salt.
Seashore paspalum
One of the most salt-tolerant lawn grasses, made for coastal sites. It needs full sun, low mowing, and a light hand with fertilizer.
A note on fertilizer
Lee County and several SWFL cities ban nitrogen and phosphorus lawn fertilizer during the summer rainy season, generally June 1 through September 30, to protect local waters. Check your local ordinance.