Glassing the Inside or outside?

Im sure this question has been asked many times before. But what do u think it's best to do, glass the outside or the inside of the enclosure.

If you take a look at the pic below, I know a shop that uses MDF as a base (brown) to start off with. Then they actually cut out a section of the wooden base (red) once they've made the shape of the enclosure on the outside. They leave about 3 inches around the bottom of the base when they cut around, and remove the MDF piece and start reinforcing/glassing the enclosure from the inside. The box was for 2 15's, to there was plenty of room to glass the inside from the bottom opening of the enclosure..

I asked if that involved more work, but the guy told me no it really wasnt, it just saves a whole lot of time sanding the outside once bodyfiller is added to the smoother surface from the fleece used to form the shape. Im sure many people think its true, Im sure there's more work involved when sanding down the box when it's glassed from the outside because the surface is a little rougher. Any opinions on this?

I actually wanted to try this on the box im workin on now. I was gonna fleece the mold I already made, then cut open a big enough section to glass the inside and then replace it, and seal it up around the cut with a few layers of glass...good or bad idea?

I thought working through the subwoofer holes would be good enough too, but sometimes you have some oddly shaped enclosures that makes little corners hard to reach.  I guess you just have to make the decision based upon individual enclosures.

ya... it can be a pain... check out how i made this part of a trunk rear wall:

https://www.the12volt.com/installbay/forum_posts.asp?tid=29540&KW=s%2D10

I filled the back after finished matting inside.