Which is easier, files or a grinder... Well, define "easier." Now that I'm proficient on a grinder that would be my answer, but it wasn't always so.
Making knives is a lot of work. There's no use in sugar coating it. A grinder sure does speed up the process, but there's a steep learning curve to using a grinder, too. Unless you plan to make a lot of knives, files or a low-buck belt sander is the way to go. If you are serious about making knives then getting a real grinder is a no-brainer.
You can move a lot of metal with files. Draw filing is a surprisingly effective way to make bevels. When I first began making knives I was actually upset that I couldn't grind a flat bevel to save my life. The first couple of knives I made I ended up draw filing to get the bevels flat and even. And my plunge lines were hopeless. I had to fix those with files, too. I was upset because I just dropped a very large amount of money on a grinder and ended up using files after all. Ten knives later I had some control over my grinding, but it took a fair amount of practice whereas it's just about impossible to mess up a knife using files if you are deliberate in what you are doing.
Lots of guys start out on a 2x42 or some such affordable grinder. Many a beautiful knife has been made on them. But sooner or later, everyone gets a 2x72. The sticker shock is enough to set your hair on fire, but make several knives with files and then look at the price again. If the price still seems crazy, keep using files. It really is about how much value you see in it, not anyone else's opinion.
I got into making knives kind of by accident. I was into sharpening and then I started reconditioning old knives. A buddy of mine wanted me to fix up an old knife that belonged to his late father. The old stag handle was cracked to pieces, the brass guard was all bent up. I ended up making a new handle and a new brass guard. When I was done it occurred to me that the only part of that knife I hadn't made from scratch was the blade. And, well, here I am.
But the moral of the story is that I did all that reconditioning with files, sandpaper, and a Harbor Freight 1x30 belt grinder that you can pick up brand new for about forty bucks when they are on sale. While I'd never recommend that machine for making knives, it has been done. And that is one machine that every man on Earth ought to have. They are just too darn useful not to have one.
This is the end result of that knife I reconditioned. When my friend gave it to me the blade was a rusted hunk of metal. It had a stag handle that was cracked all to pieces and thin piece of brass for a guard.