Verizon A1660 here with T-Mobile service...dots mostly show the same as my old 6S, very rarely one dot less than the old phone. Actual signal strength is identical, lose signal while on calls in the exact same spots I did previously, and service is great where it was great before.
If anything, the signal dots appear to be steadier than the old, but that could be my imagination too. Qualcomm chip has been good to me so far, and field test mode still somewhat works (since it locks up on the intel models).