Hi Victor,
Regarding web services access, the way to go from SAP is B1if or at least DI-Server but in all cases not DI-API.
Scenarios in B1if can directly be exposed as web-services... So from this no need of big developement Tools.
DIS will need some programming... And some tricks to make it a robust solution (i.e. reading data directly from the SQL-Server and not from DIS calls, etc.).
From my experience, but it has perhaps been changed since, DI-API will crash sooner or later, depending on the number of connections-deconnections, you're going to be limited by the number of simultaneous connections, will have memory issues...
As an example, one time I had to make a server process to download exchange rates from the web and to update sseveral databases. Since the corresponding service was not available Inside DIS I was obliged to use the DI-API. To make that stuff not crashing on a regular basis, I was obliged to move the update process in a separate program, just to be sure that the DI-API will be unloaded correctly and won't crash the next time.
Regards,
Eric