Transactional model:
1- you get all the bucks as soon as possible.
2- to do that you should price correctly your service since if you are low you cannot cover your business while if you are high you are not even able to start.
3- if you choose this model you should and/or could survey your potential clients to understand the range of price they can afford which you be better off at.
4- by this model you cannot acquire your clients' loyalty nor diversify a range of services or functions.
5- this fact does not allow you to profile your customers.
Subscriptional model:
1- you can create (and graphically you should) a rainbow of functions and services from standard to premium to be browsed ( 3 is a good number but 4 are better if you agree with giving a minimum free service)
2- you will be able to profile your costumer base from private to corporate, from age to social and etnographic features.
3- from above, you will be also able to figure out what is the most wanted and how to personalize the final product.
4- if needed you could also pivot finding a by-product without losing the primary service and business.

All the best