Honestly, I would master one discipline and then branch off later on.
As for which one, this subject is endless. I will say BJJ is very popular in UFC.
Basically this is a 'change of mind' issue. Unless they told you that it supported tagalog, or told you that the battery lasts a week between charges, then you are at the mercy of AT&T. In which case, good luck.....
The D300 is a heck of a lot better, but it shouldn't be anybody's first digital SLR, unless they are an experienced photographer.
If it is your first one, I would recommend the D40. See the link below for a clear explanation of why.