I'd go for the split wood, although the sawn may be good too. Most luthier suppliers sell little 1x2" sawn bracewood billets, which are usually pretty terrible in IME. They look fine until you split them and find that there's major runout in the invisible direction. Sometimes it's so bad that you can't even get full length X braces of continuous grain.
That said, I've bought from Alaska Specialty before, and got a free bracewood chunk (about 5" wide), which is sawn, and has practically zero runout. If it's all like that, then it's even more convenient than working from split stock, since it doesn't require as much planing smooth. But judging by the fact that the sawn wood is so much cheaper, I probably just got lucky.
If you want to do a group buy on split wood to save shipping, I'd be in for 10-15lbs
But I have enough lutz to last me a few years already, so no problem if you don't.