One is clearly more in line with the GPL.

You can’t sell code that already exists, you can only sell a license to use it. If it is under GPL you have already made the licensing choice so you can pretend to offer useage licenses but they are uninforcable because the GPL prevents you from creating those restrictions.

On the other hand, charging for a web service is actually making a charge for providing something. It is on your server, it is doing processing of information on demand, there are running costs involved. It makes sense to charge for that.

Finally, even if all the code on your web service is GPL, it doesn’t matter. You don’t have to give the code away and nothing stops you charging for or restricting access to the information that results from running the code.

(In my opinion :-) )