Free: Contests & Raffles.
If you want to hear from people with multiple spotters, you need to go to a bird forum. I spent quite a bit of time on them a few years ago when I was researching my glass purchases. Hunters know a lot about most of our gear, but birders got our butts kicked by far when it comes to optics. I have Nikon HD glass (spotter and binos). Never owned Either of the brands you ask about but I have compared my Nikon side by side with both. Vortex mid range stuff looked awful by comparison and their top end stuff looked close but I prefer what I have, maybe because it's what I'm used to. As far as swaro goes their stuff is nice but I have looked through many and haven't markedly bested my glass with them. Not bad for spending less than 1/2 the cost when comparing a hot deal to swaro MSRP. If money is no object go ahead with swaro but they don't seem to run sales and people ask for higher prices on the used market. HTH.
I own a Swaro 80mm scope and have looked through many other scopes including Vortex.My personal favorite glass is top end Nikon.It would be hard to bet againist Swarovski in that race, but the added cost is hard to justify when other optics are so good these days.I suspect that between the two you are comparing, the differences are minor and come down to personal preference as much as anything. i've looked through some friend's binoculars that are crap, and they love them. They look through alpha glass and can't tell the difference.What that means is that you are really the only judge that matters.
Maybe we need to have a spotting scope get together to compare them
So just keep in mind it's not necessarily always about image quality on quick side by side comparisons (though that's important) but generally higher end glass gives you less eye fatigue.I was able to sit behind my swaro for hours (10-12 per day) and not garner a headache.I'm not saying other glass would be better or worse, just pointing out other factors that go into choosing a spotter.