My DSs went to Knightwood, one into Y6, one into Y4 a couple of years ago. Six schools 'feed' Thornden, (the local comp), several pretty much exclusively, some less so, including St Francis. Most of the DC there are catchmented to a less well-performing secondary than Thornden.
In terms of last years KS2 SATS results, if they matter to you, their order was:
St Francis Church of England Primary School points 31.2
Knightwood Primary School 31
Scantabout Primary School 30.7
Otterbourne Church of England Primary School 30.3
Hiltingbury Junior School 396 29.7
Merdon Junior School 28.8
Not much in it, is there?
It may be of no consequence to you (it isn't to everyone) that only a handful of DC in a class are heading to a particular school but it mattered to us which is why we chose KW over St Francis, and we didn't really want a church school.
I'd say all 6 schools are 'a safe pair of hands'. All could be accused of being a tiny bit pedestrian in their approach, tbh. No one is really 'better' than the other. I'd say individual 'opinions' would tend to be based on a better or less serendipitous fit between a particular DC and his/her teacher in a given year than than an 'ethos' mismatch.
Thornden is a good school though don't be fooled by their assertion that they don't stream as they do!- mainly via exam course trajectory. The 'less able' just don't sit the exams they might not do brilliantly at. It might possibly be said that a less academic DC might be better served in say Mountbatten in Romsey, a very good school, nearby (and one without such a fierce catchment!) with a more diverse catchment and a greater choice of GCSE (IMHO). Th is very white and very MC. It gets great results, but then so it should, given its intake!
Kings in Winchester feels just like a grammar school but can be gotten into from a distance away; Westgate is considered a bit more liberal arts, is a good school but you have to be in catchment for it; Henry Beaufort is 'good' by national standards but considered the weakest in Winchester.
As stated, Perins in Alresford is highly regarded. Personally I think it stands up very well against Th and Kings!
Avoid the Eastleigh schools (sorry!) apart from Thornden.