Midi clip is just what it is. a midi clip.
A midi groove clip can be stretched to repetitive amounts.
For example: A midi groove clip that is 4 bars= 1 measure long, you can grab the lower end of the clip and drag it. It will repeat the 4 bar loop over and over again.
this comes in very handy when you have a chorus that uses the same hook over and over again.
You don't have to copy/paste 4 measures. you simply make 1 measure, turn it in to a groove clip and stretch it to gain the other 3 measures.
With midi its a piece of cake(walk)

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but with Audio, you need to make sure you have correct beats entered or it will have artifacts.
But audio groove clips have value as they retain pitch and/or BPM value.
So there's a small lesson for you my friend

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hope that helped.
PS- oh and a good way to tell the difference between a regular midi clip and a midi groove clip (or audio) is a midi clip has smooth, fine edges. A midi groove clip has divots, embedded marks to signify beats.
aesthetically they look different.