If putting together a new toy in a cartridge I don't currently load for, availability of components to load for it is my first consideration. I recently did this with a T/C Contender and went 7-30 Waters due to brass and dies being in stock at the time.
I just did the same thing again with an XP100 in 7mm IHMSA because it came with dies and brass.
I've heard good things about the 309 JDJ - if you have a source for dies and 444 brass, I'd go for it...
