I prefer all types of Low, Med and High Rate servers.
But here are the problems i have with each type...
Low Rate:
These servers in 99% of the time, will have Euro items (e.g. HeavyArmour, ExpelRings etc) and they don't add their own content untill about Lv.40. Now leveling on a low rate untill Lv.40+ will just waste my time untill im able to enjoy what they've added, and for all i know, it could be crap and i've of watsed my time.
Med Rate:
Again, the same problem, they start with euro items. These 'Med' classed exp as they think they are still take a long time, except this time, the items start at Lv.50+ for the simple fact their set exp is like 2-3x higher than a low rate, in my opinion, still takes for ages to get their for new content.
High Rate:
Right now, since there are in fact no actual brilliant, top notch servers, i play these. Although their content starts at Lv.40-50, it doesn't take very long to get their, so i wouldn't have wasted a great deal of my time to experience new content, and if i don't like it, it wouldn't matter since it didnt take long, i could just find another.
That is why right now, my mood is set to High Rates, because Low and Med servers out now aren't worth my time.