Originally Posted by attworth
The standard Mk II F should have the accutrigger (not sure if the Wally world version does.) It's also got iron sights which some people prefer, but may not matter to you.
The heavier barrels tend to be more prized for bench rest shooting, and the threaded barrel would be to add a suppressor or standard muzzle device. It's up to you to decide if those are worthwhile for your particular rifle. The Mk II F just has the 21" sporter barrel. I like this style barrel for a hunting type rifle personally. Feels a little less bulky and better balanced.
The stock on the Mk II F is really crummy in my opinion, so chances are you may end up replacing it (especially if you plan to put a scope on it.) I think the FV-SR comes with the same crummy stock, so either way you'll probably want to upgrade.
For $147 (price of the one at my wally world,) it's a pretty nice rifle. I opted for the Mk II GXP from Dick's Sporting Goods (150$) which came without the accutrigger, but has a nicer stock (in my opinion,) and came with a decent scope (which I actually promptly replaced - this wasn't the plan..)