I wish I'd asked this 6 years ago when we moved from London to Brighton!
Assuming you want to live fairly near a station to commute I would say definitely Hove - it is much more family orientated than Brighton. There is a big problem with drugs and homelessness in Brighton at the moment, the main playground in central Brighton (the level) Is often littered with beer cans, needles, condoms and worse - just horrible if it was your local playground.
Look at Poets corner in Hove - it's fairly affordable, near Hove station, easy walking distance to the beach and in the catchment area of an outstanding primary school. The only downside is the gardens are tiny.
If you want a big garden look at Hangleton which has cheaper properties but you won't be near a station.
If you did decide on Brighton then Hanover is a nice area and very family friendly with lots of good schools. It's quite hippy... you will come across many vegans and a few anti-vaxxers. You would have to walk up a big hill from the station every day though!
If you have a big budget then Seven Dials borders Brighton and Hove, is near Brighton station and has some lovely big houses, nice cafes, a decent playground and you can walk to the beach. Perfect location if you have £700k+ to spend.
Great decision btw! We are so glad we moved here.