Yes, much as Jingili states, stars can be in the name or the image they project international to be a star and sometimes there can be more of a clinically poshness with a five star as against the smaller hotels that can have a less prestigous look but at four star are very comfortable and having the same or close to same facilities.
Citadines on Bourke would seem to have all the facilities one would need/want for a good stay, the only thing I would check is that the rooms are away from Bourke St. or you ask for one that is for there'll possibly be some regular tram rumbling noise about up to MN and starting up again around 5 am and from personal experience, there is nothing worse for a good nights sleep than having something that is differently intrusive to what you are used to.
Another problem I've had with older buildings that may have newer fit outs is that the fit outs do not always extend to the air conditioning systems and there's also nothing worse to have a room which is too close to some dinosaur component of an air conditioning system, sometimes it just ductwork that is poorly supported or positioned which can see a continuous rumble transmitted and if you get a room like that, do not hesitate to ask for another.
Brady's on the other hand is a newer building so should hopefully have quiet infrastructure and though it has the advantage of being on a quieter street, last time I was in Melbourne, that northern end of the CBD did seem to have a fair bit of construction going on but hopefully sound proofing will be good.
Location wise, they are both reasonable enough in being close to tram routes and though Cetadines is more central and close to Chinatown, Cinemas and Live theatres a couple of blocks away on Spring Street, Bradey's is not too far from the dining precinct of Little Italy and there are also some nice older pubs about in the northern and north west of the CBD and some great dining options a bit east over in Fitzroy area on Brunswick St. ( a city tram will get you there easily ).
If you have any particular interests within the city area while in Melbourne, I'd just look at where they are and decide accordingly.