Hi all, first time poster - please be nice. Thankfully I am in a very fortunate position as I have received offers from two similar institutions. One comes with full teaching obligations (12 hours a week across 2 modules) which is a four year programme but the supervisors specialism is not extremely strong (compared to the second institution) however the graduate teaching assistance scheme/phd is very structured and seems to work well (with some finishing into lecturership roles). The other option is a marginally better institution and has offered me a full scholarship with 3 years funding and no teaching obligations. The supverisor here is much stronger.
Although I wouldnt mind a little bit of teaching, I dont want to be overburdened. I am more famialr with the first institution having studied there previously but I am torn between both. At this stage, I am not sure I want to neccessarily go into teaching post-PHD but I guess it would be good to have options (although I might be able to get some teaching experience at the second institution, it wont be from day one and wont be as structured as the first institution's formal programme). Does anyone have experience of a graduating teaching position with PHD or a similar scholarship that comes with teaching and how that compares with a normal scholarship? I appreciate your help guys, thanks.

I think 12 hours a week is ok, but you would need to make sure it didn't go beyond this otherwise you will lose value time for research/your social life. If you like teaching, or want an academic position afterwards, then I think the teaching one is a good choice.

My PhD was a general scholarship and I did around 3 hours of teaching a week.

I just got a temporary teaching position at a great uni :)

That's an awful lot of teaching even if it's just 2 lots of repeat seminars, especially when you factor in marking. I'd ask for specifics. If it involves any lecturing or module leadership I'd run a mile as you will simply not touch the PhD during term-time. It will also probably work out at less than minimum wage when you add in the prep time.
The other thing to think about is whether that much teaching is compatible with doing the PhD you'd want to do - you'll be lucky if it's confined to 2 days a week, so could you manage the sort of lab work / fieldwork / archive trips or whatever's needed? And writing the papers, going to conferences etc? Personally, I'd go for uni B because they're offering no strings funding, better reputation and stronger supervision. You aren't really expected to have masses of teaching experience on completion, so you could probably get enough with B. My worry with A is that you end up with little beyond teaching experience, which if you're not sure that's what you want to do could be less than ideal.