I've lived in Liverpool all my life and i'm probably going to Sheffield in September. Liverpool is, in my opinion, one of the best cities in the UK. Manchester hilariously claims to be the "capital of the north", but is grey and un-inspiring compared to Liverpool. We have character, nightlife, great culture, beautiful architecture and interesting people.
However, students that i've talked to say they have found it difficult to settle down in the city, and have been made to feel unwelcome. Also, the "scallies" can be a bit dodgy with students at times. I wouldnt say it was an overly student-friendly city. Apart from that, you can't go wrong.
I'm going to Sheffield because I need a change of scene, and when i visited I loved the atmoshpere...was alot friendlier than Liverpool. I've also had amazing reviews from current and former students who rave about the place. Sheffield is so near to the countryside with is a huge plus, compared to Liverpool which just isn't. Personally, I think i'd rather be a student at Sheffield than at Liverpool.
Also I'm pretty sure Sheffield uni has a better reputation than Liverpool uni...seems to be placed higher in league tables (if you're interested in that kind of thing).