Hi!
My Doctor for my son (now 20 months old) was Dr. Webb. I loved her! I am currently 7 weeks pregnant and am using Dr. Webb again. (November 25th is my first appointment with her because she'll be on vacation at my 9 week check-up.) She is great with answering any questions and very direct if any issues come up (which I found almost refreshing). It's very obvious that she loves kids.
When my son was born Dr. Hanlon was actually the one that delivered him (Dr. Webb had a 24 hour shift the day before so wasn't available) and I wasn't too impressed. I had gone the whole labor without any drugs and was getting very close to pushing and she encouraged me to get an epidural. The reason (which she was at least honest about) was that one of her actual patients was also going without drugs and we were basically at the same place with me being only slightly faster. She wanted to deliver her patient, but wouldn't be able to deliver us both if I didn't slow down. When I still refused the epidural she ended up delivering me, but I almost wish she would have called in another doctor instead. She was telling jokes and being very distracting....which might not bother some mothers, but I already had a bad taste in my mouth from her (not to mention I was pushing), so I wasn't laughing. :)
I haven't any experience with Dr. Channell or Oxford so I can't give any advice there. Good luck with your switch!