Hi Johnny!
In my opinion the current Alpha jackets are OK for the money, but they're really nowhere near the originals. On the one hand you have a choice of colors if you don't like sage green, but on the other hand the quality of Alpha's nylon, insulation, knits, and hardware falls well below true military specs. This has become more noticeable over the past 20 years in my opinion, and even the later issued Alpha MA-1s are a poor substitute for the brand's previous offerings. I can remember when the Alpha repros appeared somewhat better made than what's currently available, especially since they started putting that silly little tag on the sleeve pocket. I don't know too much about the Knox line, but it's possible they're a bit closer to the original type. My main gripe is with the materials used in the more recent Alpha jackets I've seen, but they may have improved this. One thing I can tell you is that Alpha's customer service is excellent in my experience.
Some of the other repro nylon jackets such as Buzz Rickson or Real McCoy's are much nicer than Alpha, but they're also considerably more expensive. Depending on your budget and preference as to color, you may be happier waiting until a good original MA-1 shows up on Ebay or perhaps the Buy/Sell page of this forum. Another option might be Alpha's Authentic MA-1 model, which is a bit more faithful to the original design in that it uses wool knits and so forth. I'm not sure if they're still in production, but I believe some websites still offer them.
Hope this helps!