Oh my goodness... I applaud you for looking for another OB! What he suggested is just unnecessary, and he really has no grounds whatsoever to suggest a c/s based on the previous size of your last baby. The fact that you had a relatively complication free vaginal delivery last time is all the more reason why you should be able to go on and do that again for this baby!
Try not to let his suggestion scare you... it really sounds like its unfounded. I would definitely be seeking a second opinion on this.
Good luck, and all the best for the rest of your pg!