I guess it depends on the cost of acquisition, I've not dealt with large companies for a while but they can be an epic pain to sell to, on the other hand the consultancy model is a hard thing to get right, the better your product is documented and easier to use the less likely you are to get the consulting work which is a kinda perverse incentive (cynically some of the the enterprise stuff I've run across seems to have lots of value and horrible documentation).

I guess it comes down to what percentage of the larger companies would want to pay the consulting/support rates, We don't pay support for anything since we largely use stuff that is well documented or very popular largely because we've been burnt on the consulting stuff before (no issue with paying a consultant on a product but when they are less technically competent than the person they are supposed to be helping that stings). Since you are the author that is extremely unlikely to be an issue though.

I guess the upside of going the pure consultancy route is in adoption, if a company can adopt your product commercially and then it becomes a core part of their offering they are more likely to pay since it becomes a critical part of their business, that's always a nice place to be - ask Microsoft/IBM :).