Summary: Personally, I enjoy the songlist in 6th Style better, but this is definitely the version to start with. 5th Style, has by far, the easiest songlist. Don't let that discourage you, there are plenty of difficult songs on there, but the difficulty curve compared to other styles is significantly less.
Summary: 6th style is a great way to start into the world of Beatmania IIDX. Right now it's still number one over my 7th Style due to the challenges and learning that Drill mode presents for me, the total n00b to BMIIDX.
Summary: By far, the best version of IIDX out for the PS2 (all to change when 7th comes our ;)). Beginner mode for the n00bs and crazy 7+ songs like V [a], The Safari, Holic [a], Take It Easy etc. All around, the soundtrack is fabulous.
Summary: Place a reservation on this title now, the more people that buy this game, the more konami will realize that this game is still worth pumping out for PS2! This may very well be the very last beatmania to be released on ps2, since the sales for 6th weren't exactly topping the charts.