Law at Reading is a very good and oversubscribed course. Plus very close to London for getting placements and whatnot at Law firms.
But yes Liverpool is most certainly a consideration for the social life. I went to Reading and it is a case of a town 'wanting' to be a city, nearly, but not quite there. There is plenty to do, but you may get tired of it quicker than somewhere like Liverpool.
Most importantly, visit them both. Liverpool is a city uni, Reading is a campus uni (a big campus, I used to walk across that beast) so hae different feels. If you come from a sleepy rural place the shock of a big city like Liverpool, although exciting, may be off-putting as well.
Study the courses as well, chances to go abroad? can interesting areas of law be studied? Ability to change/diversify your degree if law isn't all it cracks up to be? Amount of contact time a week? All important. A 'good' reputation to a course means squat if you only get 5 hours a week contact time in my opinion.