I would personally go for the 12". It'll be easier for you to access your BP with 12" so you're not reaching in 2 feet to grab him. (I am a shorty, though.) Your BP will climb higher if given the chance but they always fall.. They aren't very good climbers. A 2 foot fall may do some damage. And plus, it's cheaper.
Just my $0.02.
agreed
1.1 Het Albino BP 1.0 Banded king 1.1 Amelanistic Het Anerythristic Corns 1.1 Het Albino Western Hognose 0.1 Garter