Glass or MDF Shelves

MDF isn't great but is very benign in terms of not contributing anything particularly objectionable. Glass on the other hand isn't great either but is very hard and not very well damped at least if it is plate or tempered as opposed to laminated. With both (and with everything) how thick and what shape matters. But hardly anyone ever gives any thought to that. Instead almost always these things are made about as thick as you're talking, without ever doing any listening tests, simply because it looks about right for a shelf and they know that no matter what people say in reality they buy based on looks.

So which one looks better?

Another material you may want to consider is Corian (by DuPont). I’ve tried wood, mdf, glass, & stone, & prefer it to them. It also looks nice :-)

Thanks, so I’m thinking about a VTI rack. I thought the MDF might have better acoustic dampening properties than the frosted glass but it might be negligible . The glass does look better to me but maybe I put my Acoustic Signature on top of butcher block or something else

Have you seen the products over at:
https://butcherblockacoustics.com/
??

Really nice and relatively affordable.

The glass does look better to me but maybe I put my Acoustic Signature on top of butcher block or something else

That’s a turntable. Turntables are special. In more ways than one. What they all love more than anything is mass. A close second would be stiffness. A close third, damping. The more, the better.

With a turntable, you will be well served to give serious thought to a dedicated turntable rack. These flimsy racks like VTI that are okay for everything else are just way too rickety for a turntable. Might work, depending on your particular location situation. Or might not. You pays your money and you takes your chances....

Thanks everyone @miller and @erik 
great thoughts. Yes for more a little more money I’m really liking the butcher block to have the mass and style, Thanks very much gents!!

Buy a sheet of 1/2" 9-ply Baltic Birch plywood, have it cut into shelf-side pieces. Put constrained-layer damping between pairs of the shelves, apply Minwax Clear Satin Polyurethane (beautiful!), and install. Better than anything you can buy, easy to do.

This is an interesting company.I emailed them a few days ago and they got back to me in a couple of days.They do beautiful work,and if I hadn't been so impatient I would have purchased a platform.They use plywood and veneers.https://audiophilevibrationcontrol.com 
(I ended up with walnut butcher block)