Frankly it sounds like you have all the ins & outs down pat. The only thing I would say is that one should only consider PTD if one is guilty - not if one is not guilty.
If the decision you are making is between PTD & deferred then it is a no-brainer - PTD is better hands down.
Also, I have never heard of anyone being "offered" a PTD in Harris County. If you want a PTD, you must apply for it by submitting a packet to the chief of the court. If it gets past her / him, then it goes up the chain for 2 more prosecutors to consider. While it is easier to get than it was in the past, there are still many applications denied.
I agree with the above post, a PTD is really only an option if you believe the state can prove the case against you. If you did not commit the crime, either fighting it or deferred is the better route. If you do choose to go the PTD route, a local attorney can help you prepare the necessary paperwork and get you set in line.