I'm dissenting here and vouch for small. My NQT year was in a massive school, and despite that, I got only barely adequate support. Despite a large resources shared drive, they were not shared. Assessment stalked the halls and if people made great resources, they kept them for an assessment lesson / progress meeting.
My one form entry school knows that every resource shared is helpful. It supports our nqt excellently, above and beyond, because it needs to and they want to keep her. It is stressful having sole responsibility for a year group, but that's why small schools step up.
That said, even after nqt I like small. There is a definite team spirit, and I have found a more thorough knowledge of both key stages in all staff just because you all step up more. Plus in my old large three form entry primary, our meetings were in key stages. In my little school, I love the meetings. I genuinely love being able to track progress and issues in one meeting, and I can't tell you the amount of times I've been on playground duty and been able to inform the teacher of something because I knew about it, and knew the children, and it simply wasn't possible in my other school.
The downs are obvious. You ARE year 6. That said, small schools will bend over to help you. They need you.
Sometime it's hard not to have another fellow year teacher. Your planning is yours. But my team have shared with me their plans from when they did 6/5/4. I can reuse again more than you word think.
I like the ability to chat and manage in a small school. In my big school I got given a year group. In my small school, they play to my strength but also let me keep my 5/6 because I asked and they saw it would be good. It wouldn't be for everyone. Some teachers don't want to follow a class. For me it's been better.
And finally, it's all about the school. Get a feel. Get a look at the management. Gut feeling is real.