Just how bad are single locking tremolos?

So I've been getting into soloing lately but a lot of the solos I've wanted to learn involve tremolo bars (plus they seem kinda fun) so I'm looking to get a new 'tar with a whammy on it. I've done a little research and it looks like the whole "Floyd Rose" thing is a big giant mess...there are "licensed floyd rose"es which aren't really Floyd Roses and are built by a different company...and not all of them feature the dual locking bridge that made the floyd rose so popular. The thing is, I haven't quite been able to figure out what the difference is and why the dual locking is such a big deal. So, for those of you who have tried both...what is the difference, and are dual locking tremolos worth the extra cash?

Here's an example of a cheap guitar with a single locking "licensed floyd rose" tremolo:
http://www.rondomusic.com/SR1STDBK.html

This one has the dual:
http://www.rondomusic.com/WRL590BK.html
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