Can anyone comment on ground vs bonded Rx lenses?

I am looking for a custom Rx mask, and while I have found a lot of good advice by searching the forum there is one question that I can't find an answer to... how does a ground lens (eg Seavision) compare to lenses that are bonded to the existing mask lens? (eg prescriptiondivemasks.com)

I have seen many happy customers of both styles but if someone with experience in both could post some observations I would be appreciative. My instinct is to go with a ground lens, but if there's really no drawback to the bonded style then I have more options.

FYI my Rx is about -4, so I may need the high index lens material in a bonded mask. I don't think Seavision uses that stuff but I could be wrong.

Thanks for any input you may have!

I have both a Sherwood Magnum II mask with ground Rx lenses (Scuba Optics) and a Pro Ear mask with bonded optics (Prscription Masks). My Rx is similar to yours.

Can't say that I have noticed any difference between the two types of lenses in use.

With the Pro-Ear mask I got half lenses, with a distance correction in the top of each lens. The Sherwood mask has bifocal lenses. The magnification factor of water helps so much that I didn't really need the bifocal correction. I do have some astigmatism, but it's not a factor for me while diving. The size of the lenses in your mask will make a difference. If you have a single lens you will be limited to bonded optics. If you have large lenses, then they will accommodate bifocals better. The bonded lens has a significant step between the correcting lens and the mask lens.

Very helpful, thanks a million!