Hi Carlos,
Normally i follow the theory that the best things are normally all that you can implement after evaluate the situtation of your company... This situation contain factors or variables as:
1.- Technology: The kind of technology that your have in your hands (R3 or ECC, XI or PI 7.1 to up, etc...),
2.- Time: the time that you have, to implement the "best solution" for your case,
3.- Costs: maybe is not money directly when we implement internal projects or maybe yes, but this cost could represent the energies that you deliver with yourself with your "hard work", etc...
4.- Knowledge: maybe you have the technology, the time, the costs, the resources, etc... but if you know that you can learn how to do it, but the time is not going to let you learn, well, you will need to reevaluate "your best solution", because instead of help you the first best solution is going to complicate your project, the costs and time can increase, etc...
5.- Best practices: We have friends, manuals, forums, etc... where we can find best practices, as you are doing in this moment asking in this Community,
After those variables and reading your cuestion, i can share you may opinion, that i hope can help you:
1.- Measure it:
a) if you have the RFCs ready to be used it, and you dont have time, implement this solution and in the future migrate to better solutions, although you can sell this project requesting more time but with the condition to implement this new solution, so maybe you can change this variable and then implement web services and not rfcs,
b) if you have the RFCs, you have the knowledge to publish web services and you have time, implement this solution,
2.-Why?:
a) If we remember R3 helped us to implement interfaces with RFCs to PI,
b) The new version called ECC, supports now "ABAP Proxies", with the objective to implement a natural "SOA" with SAP PI as "standard",
c) So if you ask me, i prefer to implement a natural SOA considering web services, XML, WSDL, etc) than RFC, because here you are not using natural emisor to get a natural SOA and PI help us with their adapters to transform this RFC destination to one XML, etc...
3.- RECOMENDATION:
With the last subjective ideas, i recommend you follow the point 2, where is better use web services to implement a natural SOA (Service Oriented Architecture) than the RFC that is a technology that were used in the "R3" verions... Just evaluate the points that you need to be aware when you implement web services as timeouts, security, etc... just to solve it and then plan a "performance tunning", after this...
@note: read: "text", as one suggestion that i consider as subjective or that you can not agree with the idea and use other solution or proposal.
Best regards,
Azael Navarro Jiménez