Both were great.

Aparthotel: Not too far from ear airport, so a decent train ride to get to they attractions. Not a bad price at all. We had a car for this and used it as a base to drive places not qiute in London proper (like the Harry Potter studios)

Airbnb: Stayed in Paddington, (smallbrook mews) a short walk to Hyde park, and the tube so right near everything. No car, but easy access to a lot. Some of the places in the mews cost a bit more, but got a deal on this one. So peaceful off the street and was great as a base for doing stuff in London.