Hmmm.... I dunno.
My work PC (admittedly not cutting edge): AMD Duron 1.2Ghz, 384Mb RAM, Windows 2000, Kyro II graphics card.
My best classic: A4000, Mediator 4000, Voodoo 3 3000, Cyberstorm MkIII and a bunch of PCI/Zorro cards.
In terms of raw cpu power (handling big archives), WinUAE does have a slight edge, but a lot of things aren't as good.
The P96 UAEGfx driver is sluggish compared to the P96 Voodoo 3 drivers on the 4000. Window refresh, scrolling in IBrowse, everything is more responsive on the A4000/Voodoo, and noticeably so.
A lot of games work under WinUAE, but it just doesn't seem as smooth as playing them on a proper 15Khz synced PAL display from the 4000 (or my 1200).
Also, it does seem to have a slight latency (not slowness, just latency) that isn't present on my real Amigas, my AmigaONE with OS4, or even my friends Amithlon box.
Don't get me wrong, I think UAE and WinUAE are really nice programs, and have done a lot of good for the Amiga, I just still prefer the real thing.