Hi -- I think all three have their good and bad points - but I would advise you to also look at which is the BUSIEST. Because good, bad, it all becomes irrelevant if there's not room at the inn!
I was booked into C&W for my first - primarily because I thought my hubby would appreciate being close to Carluccio's
But it didn't work out because, on the night that I went into labour, they were full/closed. The midwife-in-charge (Mary someone) was supposed to phone back with an alternative, but she didn't - ever.
So there I was, high-risk first pregnancy (due to age and a blood disorder), 8 cms dilated, baby ready to pop and no ambulance would come because I had no hospital had accepted me.
Eventually, after googling the numbers of all the labour wards in London, my poor hubby managed to get us into a broom cupboard at St. Mary's in Paddington. And after a mad "blues-n-twos" ambulance dash across London my baby was born safely at 4 a.m. and I could go straight on a drip to prevent haemmorhaging (sorry can't spell it).
I now have have met 3 other new mums who also found C&W to be closed when they went into labour.
For that reason alone (and not because its not a great hospital) if I were to choose again, I would definitely, without a shadow of a doubt, go with St. Thomas'.
Good luck!
xx
p.s. and after sitting on the floor for up to 2 hours waiting for pre-natal appts at C&W, I would definitely recommend being seen "off-site" for these if at all possible.