I wrote this same exact thing on another thread before, but I'll do it again.....
Having a Citadel is basically asking your enemies "PLEASE PLEASE POP ME! I GIVE MORE EXP THAN 5 GOLIS!!!!!".
I'd rather suggest getting a Goli, or if you want to be really protective, get an Aegis. It's basically a goli with more HP and a little bit less firepower, but it's abilities make up for it completely and makes you really hard to pop.
If you think about it, why get a really slow URI-ONLY
ship that can hold it's own for a very short amount of time when you can bid
on the best all-around ship(Goli) or buy the next best thing to it that heals you!?(Aegis) Not to mention another hangar so you can have BOTH
of them for less than the price of 1 citadel!
Hope this helps your decision making a little bit.