Right im actually studying law at UCL and let me say this.
The course here and at Oxf are in many aspects quite similar. So dont about worry that.
Prestige- wise, honestly Oxf is better. Much. Your Career prospects wil undoubtedly be better at oxf.
However, what UCL has over oxf is our life-style. We have a great cosmopolitan life over here and we work a heck of a lot less than oxf. WE use that time to go ice skating at somerset house, theatre, clubbing in leicester sq, dinner at China Town, walking in hyde park, shpping at regent street, coffee along the thames.. the list of things to do is endless.
Also theres the ppl u meet, from SOAS, KCL, IMP, RH, RAA, LSE etc, every day theres a chance to meet some great ppl, i met one of my friends for the first time randomly waiting for a bus after drinking one night. You will always find friends here since there are so many ppl to choose from.
Put it this way, i dont like to work too hard, and even surviving here at UCL meansi have to work a little hard. so if i had wanted a balanced social life, which i do, UCL was the right place for me as it has everthing i need and time to do it.
IF you want the TOP law degree in the UK next to Cam, goto Oxf simple. UCL is not better, and is not even that close compared, though it is still excellent and one of the next institutions behind oxbridge for law. Be prepared to work as i know of ppl there doing, they churn out essays like no tmrrw and cant afford to be behind.
Here at UCL , things are very casual. If u want an EVEN easier life... goto KCL, academically not as good for law. even their students will admit it ( i have a lot of kcl friends) but atleast they get a heck of lot more time to party.. there are def times when i have regretted not going there, those times tend to be before an essay deadline on a monday morning lol