In general an SN buggy could be folded more easily than a wheelchair (with accompanying adult lifting of assisting child onto seat) but this is not an invariable rule either.
A lot of sn buggies do not fold. Ds's buggie (picture on profile) has a tilt in space mechanism, in order to maintain good posture in any position, it does not fold at all, and yet just this week we were asked to fold when we got on the bus, as there were 2 buggies on the bus already. I pointed out that ds is disabled, his buggy doesn't fold and is issued by wheelchair services, there was much harrumphing, one buggy owner refused to even look at me, and the other one eventually said she would get off the bus as she was only going to the next stop anyway ( less than 5 minutes walk away).
We catch the bus a lot, usually to the hospital. I noticed recently that the sign on the bus states
You are required by law to ensure that the designated wheelchair space is made available if a customer wishes to board with a wheelchair (or, if no wheelchair user is travelling, a disabled buggy or approved mobility scooter).
Which means that if a wheelchair user wanted to board then we would have to get off the bus, which would be a bit of a bloody nightmare, and personally I think a little unfair as IMO a sn buggy is a wheelchair. I have emailed the bus company twice for clarification of this in the last few weeks, but am still awaiting their reply.