I love to do that
I love doing that
In many, if not most situations these two sentences can be used interchangeably. But they can have very slightly different meanings too. When we use verbs like like, love, hate plus an -ING form, it generally means that we like, love or hate something while we are actually doing it. When we say that we like, love or hate TO DO something, it means that we like love or hate the practice or effect. This is easiest to show with the verb LIKE.
We usually use like to do something when we mean that we like the effect of doing something, or we think it is a good idea to do this thing because of its wider effects:
- If I need (to get) a tooth pulled out, I like to go to the dentist.
This would imply that it's a sensible thing to do. In contrast, we usually use like doing something when we find the experience itself pleasurable or enjoyable. Consider this version of the sentence:
- If I need (to get) a tooth pulled out, I like going to the dentist.
This would tend to imply that you were a bit of a masochist! It means that you actually enjoy going to the dentist.
Another way to think about it, is that when you say "like doing it" you like it while you are doing it. When you say like to do it it means you like it after you've done it.
With the verb LOVE, it's more difficult to find a clear situation where you will love to do something but hate doing it. It is perhaps possible. Consider:
- I would love to be in charge, but I would hate actually being in charge.
The information above is true for British English and for other varieties such as Australian and New Zealand English. These differences have been well documented in various grammar sources. However, it seems from comments here that for some varieties of American English, there is no difference between like to do and like doing. See F.E.'s comments below for further information.
In the phrases love to do it and love doing it, we understand that the subject of LOVE is the same as the subject of DO. Very often though, we can also find nouns that end in -ing [sometimes we can make nouns ending in _ing]. For example, there is a noun singing. Many nouns, like the noun singing, describe actions. When we use the NOUN singing and we don't say who the actual singer is, then it can be anybody:
- I love to sing jazz.
- I love singing jazz.
- I love singing.
The first sentence says that I love the habit or practice of singing jazz. Maybe I love to do it at certain times or for certain occasions. The second sentence says that I really enjoy singing jazz. In the third example singing does not have a direct object. This word could be a noun or a verb. If it's the noun then this sentence means that I love listening to people singing jazz. If it's the verb it means that I love doing the singing. If it's a noun we will use an adjective to describe the singing. If it's a verb we will use an adverb:
- I love quiet singing.
- I love quietly singing / singing quietly.
The first sentence means I like it when other people sing quietly. The second sentence means that I like to sing quietly myself.