A few millimeters makes a big difference, but the nice thing is that you can always cut bars down if you feel like they're too wide. I'd go with something that has a similar sweep to what you're riding now (assuming you're comfortable), and maybe the next step up on the rise. Not sure what's on there, but you could get a 750mm bar and play around with different hand positions - just move your grips / controls in until you find the point that's most comfortable. Keep in mind that bars that are much wider will make you feel a little more stretched out on the bike.