I suppose, if everything were even, the weighting of Reidel Vinums would cause me to have a slight preference for them. Of course, not everything is even. For $8-$10 dollars/glass I think the Spigelau (Vino Grande) are just as good as the Reidels. Amazon occasionally runs rediculous deals on Spiegelaus. The Speigelau Authentis series is very sturdy, also about $10 dollars/glass and about as good as the Vino Grandes. The difference is that Amazon occasionally charges $2.50/glass for these. I would check out their webpage to see what deals they are running.
IMO, it is a FAR better use of money to have Spiegelau Bordeaux AND Burgundy glasses than to have just one set of Riedels. And, you could really have Spiegelau Bordeaux, Burgundy, and Chianti glasses for just a little more than for one set of Riedels.
FWIW: I also have a few Riedels and whenever I have company and do a taste-test comparison, the Riedels always seem to focus the wine on the palate a bit better and produce what seems to be a slightly more full bodied and powerful drinking experience. The Spiegelaus, on the other hand, give more aromatics, more complex aromatics, and seem to produce a more nuanced drinking experience. No one has ever had a significant preference for either glass, other than the occasional preference based upon weighting.
"What contemptible scoundrel stole the cork from my lunch?" -- W.C. Fields