I wanted a black rifle but couldn't choose between the Tavor and ACR. I went for the Tavor first and after having the it for a few years, setting it up just how I wanted, I still couldn't get used to the ergonomics. Great gun, but it just wasn't ideal for me.
The mag release and bolt release could be better placed. Holding the bolt back could be easier. I also really didn't like the plastic pvc tube like grip. Also non-adjustable lop.
Sold my Tavor to buy an ACR. This gun could of been a greater success if it had more factory support. Luckily in Canada you can still get any barrel conversion you want if you have the money. For the Adaptive Combat Rifle, it really is lacking a lot of the adaptive part. You're stuck with a magpul grip that you can't remove (unless we could get the Remington version). There is an adapter to switch to an AR style stock but not available in Canada. Forend options are limited again because of the full upper rail and piston system.
The ACR does have a great bolt release location though, and overall it is a good gun. I just found a few things I didn't like, mostly the grip, stock and forend options. Even with its flaws I was looking for a NR ACR but lucky for me I found out about ATRS before I bought the ACR.
It really sucks our non-restricted options are so limited in Canada. I think most of us would be happy with a nice ar-15 and not worry about all these other inferior black rifles.
Fortunately for us a great Canadian company took notice of how limited our non-restricted black rifle options were and produced for us the closest thing to an AR-15 we can have. In some ways even improving on the design. All in the non-restricted legal status we so greatly demand.
My vote would go to the modern varmint.
Best quality, ergonomics, customization, accuracy and customer support. I will have to wait to give my opinions of the MV until they deliver mine but so far my MH has been everything I expected. I only have a few complaints about my MH so far. I like how its easy to insert the mag but its way too sharp on the edges of the mag well, I want to make mine less pointy but don't exactly wanna break out the file. The charging handle can limit some of your stock options. The barrel options are limited too, only match ss or carbon fiber. I'd love an option for a CHF chrome lined barrel. I'd also like if the trigger spring was a little harder so it wouldn't have light primer strikes with some surplus ammo. It won't feed lead tipped, round nose or other soft point bullets. One last thing is the price, its high. But it is a fair price for a world class quality product with great people behind it so you definitely get what you pay for.