Here’s my write up on this build kit after completing it and also having done a few Prefect Zero builds before…  
Let’s start by saying this is more of a short block than a build kit because even though they offer the full kit for sale, I got the one where you get slide/barrel/frame and some small parts.  
The parts come “pre fitted” and based on my kit and my research, how pre fitted they will be is luck of the draw. Regardless of how much work you will have to put into it, it’s fairly easy to do it.  
The barrel also comes pre fitted which means the lower lugs are cut and so is the hood width and length, or at least most of it. I would say overall you have to do between 20-30% of the work to get the main components of the gun working, and that is slide/frame/barrel.  
Once you are done with that, you have to fit a grip of your choice (in my case it was a BC GunWorks steel grip. You can use coupon PSG10 for 10%off) and the grip only required some filing by the trigger guard to get it to perfectly fit. I’m using an atlas thumbrest and atlas ambi safeties. Safeties required fitting to work with the mixed ignition kit that consists of a EGW hammer and sear and a Extreme Engineering disconnector. Trigger is a red dirt and Magwell is from Hales Machinery (PSG5 here).  
All small parts need to be fitted but that is also the case with the perfect zero build kits. Even though on PZ you have a fitted grip and slide to frame, on the 4.6” and 4.25” you have to fit the barrel which is by far the most time consuming part of these builds. I just noticed they started shipping the 5” with a “easy fit” barrel where you just do minimal work so going back to the Legion kit and ranking them from easiest to fit to hardest to fit, in my opinion, you have:

Easiest = Perfect Zero 5” LVL3   
Second easiest = LPWS Island Boy  
Then PZ 4.6” and 4.25”

Now as far as personal choice, the LPWS probably takes the crown. First because even though there’s work to be done, it can all still be done with regular tools. You don’t need a lower lug cutter or special gauges. Also, hybrid barrels are very hard to find nowadays and having a “build kit” that comes with one and a slide already cut for it is pretty neat. The Chiraq serrations are hit or miss, some people love the fact that the slide comes with those but others would prefer a different style so that will gear more towards personal preference. I like them. 

As far as quality, I can’t really tell a difference between them as far as the main components go. Both brands are offering very good, solid products so people like us can have some more freedom and build as we desire. 

Anyways, kind of long write up but hopefully this helps some people.   
I can’t wait to get it out to the range and then back home to prep for coating. 

Legion Precision Island Build Kit