It depends on what the speech issue is, IMO and whether the child is making demonstrable / measurable progress (how long has your child been in therapy? if more than 6 months you should have a written progress report with data).
But any child who is doing 2 speech sessions a week presumably has a significant delay or disorder. A good rapport with the clinician is worth a lot, but not if the child isn't making progress.
If you have a provider who is helping your child, that they like working with? That is gold and hard to find and worth cutting out of preschool early for, IMO.