L.S.
You don't mention whether your son has an expressive delay, receptive delay or both in addition to any other delays. The evaluation would have given this information.
My son had an expressive delay. At about 27 months he was testing at about 16 months. His receptive speech was off the charts and he had no other delays. We went the private route and used Our Children's House at Baylor and have had fantastic results. He probably wouldn't have qualified for ECI because his receptive score was so high or he probably would not have gotten the 2 45 minute sessions a week he got with OCH. I would recommend any of their therapists. I'm sure there's one in Plano. Also, insurance did cover our son's speech therapy so you should check with yours.
We liked OCH because they were very aggressive with their therapy and also involved us in giving us ideas on what to do at home, etc. You have the option of changing therapists if you don't like the one you have fairly easily. I think this would be harder with private therapy since there's typically not a pool of therapists to choose from. I imagine this is also possible with ECI. OCH also does PT and OT there if your child has other delays or issues. My friends who did private therapy at home were not very involved in their kids' treatment. ECI might be different though.
I have friends who went through ECI for OT and ST. They were, for the most part, happy. I think they're especially good if you have a kid with more than one delay like my friend had. ECI therapists come to you which, for some, is a bonus especially if you have more than one kid or can't drive. They can sometimes be harder to get someone out and you may have to wait. We did have to wait a few weeks before we could get in for an evaluation at OCH though, but once we did we were in.
ECI is sliding scale so that is very nice, especially if you have insurance that will not cover ST. This would be something to consider in your decision of course.
Good luck!