Hi lucyk. I live in Cardiff now, but Stratford is my old home town, and I also know Wawrick. I prefer Stratford - more shops and a lot more going on. It has its own little cinema, the theatres, loads of good shops and is lovely for pootling round with kids. There's enough McDonalds and coffee shops for teenagers to amuse themselves, and a really good leisure centre too. Property is more expensive there than Warwick, but affordable if you don't want to be right in the centre. There is lots of new-build going on at the moment, so you may be a ble to find something cheaper there. Lots of them are along the Alcester Road - same road as the High School. Warwick is much quieter with a very small town centre, but St Nick's park is lush. It is also only 5 mins from Leamington Spa which has loads of shops and a cinema and all that. Have you considered looking at Wellesbourne - a large village about 10 mins from Stratford and Warwick? Much more affordable housing if you don't mind a bit of a drive, and enough in the way of pubs and corner shops to make do.
Stratford also has a brilliant facility - Stratford Music Centre. This is a weekend thing held in Stratford College (also v good - does loads of BTECS, A-levels etc) and I loved it when I was a teenager. You can learn anything from rock guitar to tap dancing, they do annual shows and loads of drama. I made LOADS of mates there. It has lots for adults too, so would be good for friends for you too.
Secondary schools are excellent in both places. Stratford has grammars for boys and girls (girls is Stratford Girls Grammar, and boys is King Edwards) both of which are excellent - they are always in the Times top 100 secondary schools list thing. Stratford High has just been totally rebuilt in the last year to the tune of several million so has top notch facilities. Warwick has 2 excellent private secondary schools - Warwick Boys school, and King's High School for Girls. There's also Myton High and Holy Trinity. Not sure what they are like. Kenilworth is a small town near Warwick and their high school is also very good. There is another grammar at Alcester, which is mixed, smaller and just as good. Alcester is a sweet town just 7 miles from Stratford and might be worth a look for housing.
Hope this is all useful. I'm so jealous - I would LOVE to move home, but there you go. I'll keep an eye on this thread in case you want any more info.