I have a 2700uv, a 2700 and an fx5 and the fx5 is a far better filter in every aspect, actual flow rate is higher than the 2700s, filtration is superior ,auto primes, auto purges daily, bottom drain, less power consumption, i even like the look - but it is in the next price range after all. (can find for 250-350 2nd hand, occasionally)
Also I would definitely prefer the 2700 over the 2700uvc because the paltry 5w uv unit is not a benefit when you realise you have sacrificed the priming system to house it, not to mention an extra 50 bucks, which would nearly buy you an inline 9w uv sterilizer.