Southern Folk Chime in on BTU!

[GolfStream]

I'm considering upgfrading my 2006 19 foot Bambi for a 2007 28 foot International (I figure if I'm going bigger, I'm going for it.) I have found two units and the only difference is the BTU's on the A/C. Does the 15000 BTU a/c cool down a 28 foot international all that much faster / more efficiently over a 13500 btu unit??

I LIVE IN SOUTH FLORIDA. GOOD AC IS A MUST FOR FOUR TO SIX MONTHS EACH YEAR.

thanks!