We here at Sparkling Stemware have tasted a lot of wine. Believe us, esthetically speaking, there is nothing like swirling and drinking a Mouton-Rothschild from a gigantic 35 oz. crystal-clear, featherweight bowl. So, there you have point number one, hand-blown wine glassware will almost always be lighter and have a thinner wall when compared to machine made. This only makes them more fragile. Its great if you're spending $600 on a bottle of Bordeaux in a restaurant, you might be a little jaded if the Sommelier doesn't bring over the $90 Riedel glasses, but is this really practical for dinner parties or for busy restaurants?
Fragility is the issue. We have all heard stories of expensive hand-blown crystal shattering just from being looked at the wrong way. The stems, the neck and the glass walls are just not built for durability. Machine made crystal is therefore much more durable. As far as the glass itself goes, it is inert matter. The glass does not care which shape it is formed into or how it was shaped, so this is a non-issue. Some will say that the glass affects the taste of the wine and given that lead acetate has a sweet taste, it is better for the wine. This logic is of course completely false.