What's the difference with these 2 small cutters??

[wantboost]

Here's a pic of the two. 
Should I also get a 3/4 one?

[NoDIY]

It combines sized adjustability with this type of cutter i beleive. Kinda cool

https://i.ebayimg.com/images/g/QJgAAOSwn35aoVY1/s-l400.png

I have used one similar to this one pictured

[wantboost]

What's the different with the left and right one in the pic

[NoDIY]

I believe the one on the left combines the function of the right with the functions of the one I posted.

Edit.
Video here demos it. Auto tightens

https://youtu.be/qetLFEKzQoc

[wantboost]

I guess I will need a 3/4 one also ??

[bster352]

I guess I will need a 3/4 one also ??

No you just need one. It adjusts up to 1" so any pipe 1" or less.

[wantboost]

Ok I guess I should spend the extra money and get the autofeed

I guess I will need a 3/4 one also ??

No you just need one. It adjusts up to 1" so any pipe 1" or less.