Best is relative. Here's my take on things after about 30 years of fretting guitars:
Nickel Silver is great. It's easy to use and bend/radius, easy to cut, easy to file and crown. It is the softest of the three materials and will wear over time, requiring fret leveling or refrets, eventually. How often depends on how often you play the guitar, your grip, strings, and how hard the fretwire is. I really like Jescar and StewMac wire. They just feel harder to me than does what I get from others. I prefer to cut and radius my own fret wire. I over radius it slightly, so that when pressed or tapped in the barbs bite into the wood and prevent it from springing up. I also prefer to glue my frets in with super glue. Fret slot width compared to tang width on the fret is very important. If the tang is too wide or the slot to narrow, you get compression. Fitting the fret in the slot presses outward on the walls of the slot and can cause back bow. If you know how to control this, it makes it nice to remove some bow out of an old acoustic that does not have a moveable truss rod. Also, fret tang length vs. slot depth is important or your frets won't seat. I highly recommend if you've never fretted a guitar that you purchase the Dan Erlewine video #1 on fretting basics. It's $50, but it can save you a ton of money and heart ache. I was given the video a few years ago (after 25 or so years of fretting) as a birthday present from a sister-in-law who knows I love guitars and fretwork. I watched it and realized the value of this video for beginners/novices. It has a lot of helpful info and is great. I recommend it highly over youtube videos, although there are some good ones. It's broken into chapters you can jump to.
EVO is becoming my favorite. I put it on one of my guitars and loved it. It's harder than NS fretwire, but not quite as hard as stainless steel. It's a little tougher to bend and work with, but not too much so. I like to radius it just right or just a hair over. It's hard enough material that you might get some up-spring from it. If you use super glue, it will hold the fret down. It does not wear as fast as NS wire. It is easier to work with than stainless and holds up very, very well. It's the perfect middle ground between NS wire and stainless steel. It doesn't seem so hard to file and crown and isn't as hard on tools as stainless is. I really like it a lot, but enjoy the ease of working w/NS wire, as well.
Stainless is very hard material. It needs to be radiused to match the board. If it's under radiused it will spring up on the ends. If it is over radiused it will spring up in the middle. Glue helps, but it can still be hard to mash down into the slot and you have to hold it for a while. So, make sure it's radiused just right. It is harder on tools and, at least for me, my hands. I've had some wrist injuries as a kid racing BMX and skateboarding on vertical ramps, so that's my fault. But it is harder to cut with nippers. The best nippers are still the ones StewMac sells (others correct me, but I've gone through all types and these are still the best). I used the same set of nippers for over a decade or two before having to replace them after only a few stainless refrets. It is harder on files, as well. It's hardness results in the extra work it takes to get the frets just right, so I charge more for stainless refrets based on the extra time and effort it takes. It's hardness also results in it lasting way longer than anything else. There's a gigging guitarist that I refret all of his guitars. I used to refret his strats once every 8 months or so (he plays a lot and relies on only a couple of guitars if he can). He switched to stainless and I have only had to do a fret level on his number 1 once since I refretted with stainless 2.5 years ago. It lasts. It's not permanent, but unless you gig 4-5 nights a week and only use one guitar with really heavy hands and 12 gauge strings, you probably won't need to replace it.
Most of the quality in a fret job is fret slot/fingerboard cleaning and prep, and then leveling and crowning the frets. That's the meticulous part. The cutting and pressing/hammering in is the fast part for me. Always clean the fret wire, and I recommend buying a proper fret bender to radius the wire. I have built many of my own tools, but I have also tried the tools many others use. I would recommend the StewMac fret bender (of a very similar one you can find on ebay). I rely on that thing a lot. I also recommend good nippers and files. Don't cheap out. The tools will cost up front, but are worth every penny in the long run, and every extra minute. Some don't like StewMac b/c they are "pricey." Well, I often hate the phrase "you get what you pay for," but it's true. Most of the fretting tools you can get from StewMac are high quality compared to some of the other crap out there. I experiment with tools and equipment, and a lot of their main tools are good. I like their fret files, diamond files, nippers, and radius tool. If you get the Erlewine video from them before buying tools, he shows you other tools you can buy or make to save some bucks.
Good luck, I hope this helps. I am open to the opinions of others, as these are merely observations I've made in my many years of working on guitars and refretting. I can always learn something new and reconsider my stances if provided a well-founded opinion, so don't take what I say as gospel, anyone.
How critical is it to Pre-bend nickle silver fretwire to an exact radius? I got fret wire that is coiled as opposed to straight lengths. Do you just need it bent a bit tighter than the fretboard or exactly __ inches tighter radius ? My fretboard radius is 12".