I've seen two different types of jigs for 80% that use a router to mill out the FCG, the Modulus Arms HD, and the EZ Jig. I just want to know which is better, and why.. The ups and downs to each....
Currently the Modulus Arms HD is on sale for around the same price as the EZ Jig with Steel bushings. In the future I may want to try billet lowers, but I wouldn't want to do anything too extravagant.

Modulus hands down.

I have both and each one has an advantage. Modulus has the steel sleeve inserts which is nice. However now that I use a mill for my FCG pocket I only use the 80% Arms side plates to hold the receiver in the vise. If i was going to do everything with a drill press and router then I would stick with the Modulus.

If you want to do billet lowers I would get the Modulus jig.  The EZ jig doesn't fit billet lowers such as the New Frontier or the Iconic Industries.  The modulus has a guarantee to fit any lower.  I've used the original Modulus jig on both the New Frontier and Iconic lowers without modification.  I would think the Modulus HD jig would also be GTG on these billet lowers.

I've done several billet and oversized poly lowers of different brands with my Modulus HD jig and it fit them all with no problems.  The Modulus HD jig has steel sides and top plates, and it really feels solid and works well.  If you get their Speed Drill Kit you really don't even need a drill press.  I do recommend a drill press vice (not that expensive or big) and maybe a big C-clamp to clamp it down to your work surface.

No experience with the EZ jig but I've had my Modulus HD for a little over a month and I've been using it quite a bit and loving every minute of it. The first couple took a while but I've got the hang of it now and this jig is tough and very well built. I've ordered the speed drill set to see how that goes, thankfully I do have a drill press but for the heck of it tried a couple holes with hand drill and boy that took some effort. The drill press vise is also a must. Got mine for around $20 and it works great.

You'll be surprised how much easier it is with the Speed Drill Kit...  the small 1/4" drill goes in easy...  and once that pilot hole is drilled the 3/8" goes in like you were drilling into butter.  It really does make it about as quick to do with a hand drill as it is with a drill press.  Also I have done a few lowers only drilling one hole, the one straight through the trigger slot.  So that is an option too.

What if you ignored the price difference... would you guys still recommend the Modulus HD over something like the Easy Jig HD?

The thing i can see that the EZ jig has over the Modulus is the engraved drill bit size markings - just in case you forget and are too impatient to look it up.

The Modulus, however, includes their tool depth guide jig which I find significantly more useful than those engravings.

There are only 3 drill bit sizes and they are pretty obvious...  5/32", 19/64" and 3/8" so I don't consider not having the size engraved a big deal.  Maybe it might be if you supplied your own tooling rather than buying Modulus's kit.  Even then it isn't hard and only the 5/32" and 3.8" are critical, you could probably use a size smaller in the 19/32" and still be O.K., as that one is just for the one that goes through the trigger slot and it will be milled out bigger anyway.

For me the big thing is, even though I've heard that the 80% Arms guys are also good on customer service, the Modulus guys are supporters of this forum, active here and I've seen their customer service quality -- every time someone has had any kind of issue they've always been quick to do whatever they can to make it right.  I've never had any problems so that is all the better for me.

Take a look at the Daytona Tactical Jig.

That jig will not work with a router.

This is correct.  Daytona Tactical is a drill press jig.  It is cheap, but it isn't even in the same league as the Modulus HD or 80% Easy HD jigs...  it isn't anodized.  It doesn't look like it has steel side or top plates or even bushings, it doesn't look like it is universal fit either.  It basically looks like it is only a couple notches up over something like the Stealth Arms jig.

If you really want a quality drill press type jig, the one from Broken Arms is in my opinion one of the best...  but it is not cheap.  http://www.brokenarmory.com/AR15-Lower-Receiver-Jig-Jig.htm

By comparison it is anodized, has more drilling plates and it has hardened steel bushings.  If there were no router type jigs, I think it would be the one to have.

Personally I've been completely satisfied with my Modulus HD jig, and my 2nd choice for brands of jig if I had to switch would be the 80% Arms Easy HD jig.  I'm sold that the router approach beats a drill press hands down for the milling operations.