Talk to the school you're considering doing this at. You may be able to recieve credit for cross countries if they meet the criteria of lessons in the curriculum. We would do this for students if they came in with prior experience to complete a rating. Saved them a little money and some time.
Most 141 commercial programs are going to be very similiar. In part 141 you can see the requirements for ratings and see how they compare to part 61. In most cases 141 will require the same cross country experience but does away with much of the total time requirement.
I did most of my training 141. I instructed both 61 and 141. In most cases the structure of a 141 course was the saving grace. Often students that were completing ratings 61 took things at their leisure, and it would end up costing money in the long run. Get in, get done, move on.
If you're considering instructing, you may want to take the time to do a private multi ride somewhere in your training. The reason for doing this would be PIC. All your remaining training would be loggable as PIC. Spending a couple hundred bucks to do the checkride could save you tons when you're looking to get the MEI later and you need the multi PIC.