The large majority of Second Life folks use Firestorm. For me and likely for most of the others from comments made on these forums -- it is not about performance, it is about FEATURES. There are dozens of FS feature that I use everyday and do NOT want to be without. When I had to use the Linden viewer briefly to upload complex mesh (apparently that isn't something we have to do from now on --- happily) it was oh so
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Firestorm vs the LL Viewer
in Second Life Viewer
Posted
What do you mean by the features