Yeah, financially there is a big chasm between a typical GTP and PGCE student. This is part of the point of the program - to provide a more financially rewarding route to being a teacher for those who have been working in industry and have commitments (mortgage/kids etc). Im a bit of an anomaly being a 23yr old GT. Normally, Golden Hellos are £2500 and the PGCE bursary is £6000 which gives you 8.5k total (minus uni fees) - for maths and the some sciences these are £5000 and £9000 respectively which gives you a much healthier £14k (again, minus fees if your unlucky). As a GT you get £14.5k salary minimum, more if you have significant experience, and have no university fees to pay. So as a maths student im a whole £500 off by being a GTP student rather than a PGCE student. However, since I have to pay council tax because a GT isnt considered a full time student its basically the same.
As a GT I spend most of the year in my main (secondary) school. I go on 3 placements - one, a 6 wk block in another secondary school that must be significantly different from the main school (ie. my main school is a typical comprehensive, my second school is a grammar school). I also have to do a 1 wk 16 - 18 placement (college) and a 1 week primary school placement. I dont know how many placements a typical pgce student will do, but im fairly sure it is 3: 1 per term of varying lengths. However, Im not sure there is any guarantee of your placement schools being 'different' - you could end up going into 3 comprehensives that basically have the same student make up/result figures. Im also not sure if PGCE students are required to go into post 16/primary schools. In any case, a PGCE students 3 placement schools to a GTs 2 shouldnt be that much of a factor.