HPTuners
HPTuners is the only tuning software that supports the 3800 that is still being produced. It has the most features and is the easiest to use out of the box, however it is a bit more limited than using TinyTuner and DHP.
Another benefit of HPTuners is that it can be used with nearly any GM vehicle that uses and OBD2 port. DHP is only capable or tuning ~96-03 GM V6 PCMs.
Cost
The HPTuners interface costs $300 for the most basic version. This version is good for reading and writing to the PCM. It can also log, but it's not able to log additional inputs. To enable more logging capabilities you would need to purchase the Pro version which costs $600.
HPTuners also requires you to purchase credits to unlock the capabilities of tuning a PCM. Each PCM requires 2 credits to register it to an interface making it one of the most expensive ways to tune the factory PCM.
With HPTuners, it will cost at least $400 to write a tune to the PCM. If you want to log additional inputs such as a wideband it will cost $700.