I'm not sure we have to complicate the matter. I'd say gerund, period.
Complicated for whom? Teachers or pupils? Sometimes in the sake of simplicity we might derail only for later on have more problems and the students more doubts.
I find it simpler and more logical than having to memorise lists of verbs which are followed by to+ basic form or the -ing form.
Thank you José, you have brought up a problem with teaching the catenatives as lists - it tells the students nothing about the meaning of the verb used. Learning lists will leave the student with the impression that the choice between gerund and "to"+infinitive is arbitary like the choice between masculine, feminine and neuter nouns in some languages. There is an important implication about the meaning of the verb used and students should know that. In my experience, students learn the different forms more easily as a result.
As always with these things you have to decide whether you are talking about:
1. the activity itself - in which case you use a gerund, or
2. the intended purpose - in which case you use to+infinitive.
Andrew, how could you explain when we get the basic form only (AKA the bare infinitive).
(1) She watched (saw/listened...) the children play.
I am aware that the -ing form can be used here.
I partially answered this, José in "transitivity-intransitivity spectrum," but this is a far more specific case.
"Watch" is a little difficult for me to understand, it appears to be one of the verbs of passive perception, although when one watches something, one clearly directs ones attention, which is not done when one mearly "sees" something.
The other verbs of pasive perception include: see, hear (but not listen!), sense, feel, and witness.
Perhaps the sense of pasiveness is the idea that we choose not to join in.
Either way, these verbs can be followed by the object and bare infinitive. This is something they share with "have", "let", "make" and "help".
"Watch" and the the other verbs of passive perception can also be followed by the object and -ing form.
The difference is that when an object is followed by an -ing form, it forces the -ing form into the role of present participle rather than gerund, that is to say, gerunds can be substituted by "it" the present participle can't because it does not have any substantive meaning:
Compare:
I like playing -> I like it
I watched the children playing -> * I watched the children it.
This also applies to "be", "come" and "go" without the object
I am fixing it ->*I am it it.
Come dancing ->*Come it.
He's gone fishing -> *He's gone it.
The difference then.
When followed by the object and -ing form, the we draw attention to the continuous nature of the play, when followed by the object and bare infinitive, we don't.