I lived in SE Texas for years and kept (and bred) rubber boas with no problem. I have since moved to San Antonio, and my rubberboas are doing fine still.
They are a truly underappreciated snake. They are very hardy, easy to keep and predictable captives, as long as you deal with captive born animals. Babies can be a little tricky to get started on pinkies, but once they do, they eat them readily.
They are also easier to keep at room temps as they don't require any sort of extra heating. Mine eat readily at room temps from the mid 60s to mid 70s with no access to any sort of external heatsource.
Boa constrictors are going to be available more widely in a variety of morphs. Some of the prettiest morphs (Surinam, Guyanan), unfortunately, get quite large and have the most unpredicatable temperaments. "Colombian" Boas are generally smaller and more docile.
These are very different snakes. Rubberboas are small snakes that can be kept at room temperature, but they are shy. If your goal is to "look at" your snake a lot, you will find that your rubberboa isn't visible much of the time (perfectly normal behavior for most snakes). A boa constrictor will sit out, particularly when older, although they aren't particularly active. If you give a boa a hidebox, most boas will use it until they are 4-5 feet long.
Boa constrictors are considerably more expensive to house and feed. A female rubberboa can live her whole life in a 10 gallon aquarium and would cost between $1.50 and $3.50 a month to keep fed (depending where you buy your rodents). A male would cost significantly less as they are much smaller.
A boa constrictor will require much larger cages (minimum 4x2x2 feet) which are more expensive, take up a lot larger room in a house and are difficult to clean. An adult boa will cost you around $10-20 a month to feed. Boas also require access to the appropriate temperatures (75°-85°F) all year long. This means you have to keep your snake room at 75° all winter long. This is warmer than most people normally like to keep a room in the winter. With rubberboas, you can simply let them cool down into the mid 40s to mid 50s and let them hibernate.
They are both good snakes, but are very different. The suggestion about a Rosyboa is a good one as well. Easier to keep than rubberboas, more widely available, but still small and very docile.
-----
Chris Harrison