I've been perfectly happy with my 425XL, but I guess the extra 12" in length would make the tang police a little less concerned with your stocking. Lighting will be a little more expensive for the 525 - if you go with LEDs, I'm assuming you'd need two fixtures, rather than one.
In the other hand, if you can afford it, in this hobby it's always better to go bigger.
Either way, I think the Red Sea Reefers are great tanks.
Good luck,
Kevin