Hey,
Well for starters and I'll keep this short. Sumatran red bloods and Sumatran short-tails and Borneo short-tails are all different species. Yes! they are very closely related and were at one time linked into a taxonomic group formerly known as the Curtus group. However, after much wrangling and investigating by the experts, it was determined that the entire Curtus group ought to be divided up and all given separate species identification. The outcome being that they are no longer considered sub-species of one another. Sumatran bloods and any other red blood for that matter is still a blood and identified by the scientific moniker of Python Brongersmai. Borneo short-tails, found only on the Island of Borneo are called Python Breitensteni, and lastly but not least, the Sumatran short-tails or Black bloods, are known as Python Curtus.
If you are looking for a nice fat animal that does not get too large in the way of length and will be reasonably manageable once it attains adult size, then a Borneo short-tail is probably the better choice for you. Also considering the fact that they are much more tractable for a newbie to work with than would be say a red blood. Also, females get larger than males do in any of the aforementioned species, so that is something to consider too.
Good luck with your choice.
-Angel
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In life you can fall many times, but you're only a failure, if you don't try to get back up!
Evil Canevil