They have very different attitudes to setting/streaming, at least in non-Covid times, so that could be worth checking out, if you think you prefer one or the other. Parkside doesn't set much, if at all. (Some in GCSE maths years to split into F/H tiers). Parkside is also v keen on triple science. Not so many option spots left. I don't know if things have changed re. travelling. It used to be that many Parkside students cycled to Coleridge for options like Drama, PE, etc and some did the reverse journey. It was always at break/lunch so they had time to do it (only a 10 min cycle - they also did Cyclability training level 3 in Year 7 to make sure they were competent cyclists). I don't think they go to any of the other sites for lessons, but occasionally for special events. They use Parker's Piece for PE lessons, and at various ages, the pupils are (were) allowed out there or into town for break, lunch, etc, which they quite enjoy. (Probably not happening this year of course)
Chesterton does more setting, and even some sort of streaming I believe, with some Year 7s who need extra work on English and maths following a somewhat different timetable with fewer/different subjects and more English/maths. In other years, the classes are differentiated by the expected grades (e.g., a 7-9 class, a 6-9 class, etc). It's much much bigger and everything on site, including the sports centre, which they can join to be able to use the gym etc after school. They have quite a lot of facilities for music, and possibly the fact that they are bigger means more different ensembles. Both schools have offered additional maths courses for top GCSE students in the past, but I don't know if that has changed because of Covid.
Both seem to get v good results.