I can only speak of traktor, but I mix with flac and wavs only as the sound quality on 320 mp3s is noticeably shoddy when compared upwards. It takes FLAC and Wav fine.
So far I have 65GBs of music on traktor but I'm constantly removing tracks I don't need as I upload more. Traktor does take some tweaking in the settings to get going well but that is easy once you have sussed it. I only really use a fraction of its features, but there is all the loop functions you would need, up to four dexs, tonnes of fx and loads of other things on top of that.
One thing i must say about traktor is that it is prone to the occasional spazz out. Its deleted all my music saved in traktor on more than one occasion. But everytime you use it, it sets a backupfile so you can revert back to an earlier save point (last time you used it) if it does that. This will save all ya tunes and settings so its just a case of a few clicks in the relevant folders and its back.
I have plenty of advice on getting traktor running well and how to keep one step ahead of the spazz mode, so if you plump for that one i can give you some tips if you need it.