I prefer prong settings over basket. I think they help the stone pop a little more. I can''t explain why I feel that way, but I do.
As for 4 versus 6....that depends on a lot of factors. Some people think 4-prongs make a round stone appears square, although I have two 4-prong rings and neither of them looks even remotely square. One of my diamonds was originally set in a 6-prong and while I liked the look, I would prefer less metal on my diamond so that more of the stone is exposed.
Well, now that I have my larger upgrade stone, I sometimes wonder if I should''ve put it in a 6-prong setting for extra security. If one of your 6 prongs comes loose, you''ll have redundancy and will probably not lose the stone. However, if one of your 4 prongs comes loose, then the odds of losing your stone are much higher.
If you end up with a 4-prong setting, just make sure you have the prongs checked by a jeweler every 6 months. HTH.
I''m not a big fan of the way the prongs come to a "V", but that''s just my personal taste. I also like that the baskets are less common, so not everybody has it.