It affects signal very well, cuz glass dishes usually (and particularly those made in the USA) made in such away that they keep their shape close to original over a long period of time.
So its a positive? better signals and longevity?
Same size primefocus and offset antennas perform exactly the same if used with proper feeds....IMHO
I meant the material not size.
If the glass dish designed for reception in Ku-band, it will perform same as solid metal dish. Glass dishes have metal mesh imbedded inside. So, solid and offset dished will perform the same if they both designed for reception in the same band, such as Ku-band. But, usually, glass dishes are all designed for Ku-band, some of them are OK for Ka-band. And, of course, they all be OK for C-band.