Me and friends started on Loraderon, but we switched to Deathwing for the following reasons:
1. No queue
Waiting 1-2 hours in queue every day is a joke, getting disconnected and end up in queue is a joke. This basically means you can't play when you want and if you (or maybe the main tank) get disconnected during a dungeon or raid, oh well, tough luck.
2. Rates
For people like me who have played retail for years (read leveled tons of chars) and like to have more than 1 char, leveling at 1x is torture, especially on a private server, especially on a private server I can't log in to. At first I was critical to the 7x rates on Deathwing but now I love it, leveling still takes time and effort, but a lot less. For example, each level 71-80 takes 30-60 minutes of focused questing.
3. Random Dungeon Finder (RDF)
With no RDF and 10,000 people online, spamming the global chat, each player trying to be LOUDER than the previous players, it's not easy reading a flashing wall of text and finding whatever it is you're looking for, or offering. Also, once you find a party, you have to fight who goes there to summon, it's a waste of time and removes an important part of the WotLK experience. This is a major fail in my book.
4. Marketplace
Loraderon doesn't offer heirlooms, it doesn't offer name change, faction change, and so on.... and for the stuff it does offer, prices are much higher compared to other realms.
5. Lag
Loraderon with 10,000 players online lags, feel free to browse the forums for tons of lag related topics. I believe this mainly affects PvP players who tend to be more sensitive to delays.
6. Random disconnects
There are at least a few random disconnects most days, if not every day.
7. Quest objectives
Since the server xp rate is 1x, you don't have the luxury to skip many quests. At times you will find yourself waiting and fighting other players for quest objectives on 5-10 min respawn time.
BUT, Loraderon is not all bad even though it could have been a lot better.
One of the good things about Loraderon is the core - I'm gonna be honest, Deathwing is bugged as hell - but they have plans to patch Deathwing with the new core. Another good thing Loraderon has is that it's pretty new and people don't expect you to have 99999 GS.
For me, the perfect private server would be a new progressive realm with the latest core, RDF, heirlooms, 3x rates and ofc no queue. I would even pay monthly fee to play on such server.