I too feel this way... I have waited so long, and have been preached to by SE about this even ground starting as well, so I will be going to a fresh new server. Just off the top of my head, these are some of the pros and cons that I have thought about that comes with joining each server.
Fresh Start Servers:Underlined Text
Everyone's on even playing ground starting at level 1
More of an adventure as everyone is joining and teaming up to figure things out.
A real since of grinding, since no one is power leveling people, or crafting others the best gear for help. So less leeching.
No initial hating on jobs... ie... we don't need a brd, we need this setup to win blah blah blah.... lol because know one will yet know winning strategies, which also kinda goes with people on even playing ground trying to figure things out.
No jerks looking down on you because you don't have 6 level 50 jobs yet, amongst other things.
Less higher level players to look up to for advice.
An economy that will take a little time to get going. Less items in the AH. Mainly npc gear for the beginning until the crafters of the server become of age. LOL
No high level people giving you hand me down gear, or being able to help repair your gear at early levels. Kinda goes with the crafting and economy situation.
Legacy ServersUnderlined Text
Many high level people to help you with stuff, and be able to give you gear, and help craft you things.
Many establilshed Free company's to choose from that already know what they are doing.
Options of being power leveled I guess by high level conjurers and White mages
May level up through the game faster because of help with high level players
May get help with money from friends. Kinda goes along with the crafting and economy.
Maybe low level crafted items more available in AH. (can also go with economy as well)
Will feel like your playing catchup, being told where to go, who to talk to, where to start and finish missions instead of figuring them out. Have high level help who can defeat easy quest for you, and may make you always ask others before doing things, cause you know they are experienced.
Lose the feeling of that fresh start with everyone being on the same level and same page. A feeling rarely witnessed by players at the start of an MMORPG
Being told which class is best maybe, and which class you should be leveling due to a free company already having a lot of the jobs you are interested in... IE... free company has 8 high level, cold dragoons and feel you should level conjurer because they only have 2...
Basically though... when I think about it, it really comes down to two things. Do you want to be able to rise up, meet other newbies along side you, and draw swords and learn with these new found friends? Or go somewhere where you drop your mouth at the cold level 50 man beating everything, and getting stronger, and people playing endgame content, while you play catchup only looking forward to the end game, and racing to catch up so you can play with them, not truly enjoying your lower level days trying to figure stuff out. lol
Of course these are just my opinions, and I've always wanted to know even more Pro's and Con's to both. But I have decided that I'll join a brand new server over the established ones.... How can I make money doing my little level 5 craft, while level 50 craftsmen have flooded the market with that lower level stuff for cheap because they don't want it anymore, and are trying to save inventory space. lol