Well I have had both, but my super expensive DSA did not want to seem to cycle anything and I did not feel like trying to spend ages "fixing" a gun that cost $2,000. Anywho I will limit my observations.
What I like about the FAL
- better ergonomics
-better weight distribution. Although they seem about the same weight, the HK91 seems a bit more barrel heavy and when you add a bipod, just shouldering the thing for one mag because difficult.
-FAL breaks down for cleaning really easy, the gas piston is very easy to get out and clean ( its the same system used on my FN49), the reciever pivots up so you can extract the bolt and carrier without doing much.
- Fal can have better sites. My DSA came with very nice adjustable sites similar to that on the M16...some of the cheaper fals look to just have a simple peep site though.
-Changing mags seems alot smother as you just rock them in like an AK mag, and the release is nice.
What I did not like about the FAL
- can't commend on function much since thats where my problem was
- hated the placement of the bolt handle. It is not far enough forward to give you the leverage you need to open the bolt on a stuck case. I thought it looked like it was in a great place when I saw pictures of it, but in reality is was horrid. An AK or HK91 bolt handle give you much more leverage. It especially sucks for a right hander.
Now I have one of the early century HK91 clones ( which is very well made) and I would not part with it.
What I like:
-function wise its a very simple stamped design, very reliable
- it will eat any ammo I put into it, even the cheapest dirtiest russian ammo. Since I do not reload, It does not matter to me if the cases are dented.
- accuracy is just fine for me. I am at 300 meter shooter at the max ( bad eyes and such) so it will preform just fine at those ranges. Accuracy is better then an AK but its not going to win any competitions.
- Cheap mags, granted I only have 10, but if I wanted 100 it wouldn't be that expensive either.
- very modular. swapping out a new fire control group, new furniture, you name it, can be done very quickly. basically all you do is pop out one or two plugs ( which can be done without any tools) and your part comes off.
-lots of aftermarket parts
-cleaning is easy, not as easy as the FAL, but still pretty easy.
-decent sites, that drum sites take a bit of getting used to, but do work.
What I do not like
- as I said weight distrubtion can be a problem
-optic mounts are a problem for both guns. For the FAL you can get a rail, but they are not that cheap or easy to install from the looks of it. on the HK91 you can get the Claw mount which is easy to put on and take off, but they are not cheap either.
- recoil seems a tad bit harsher then the FAL.
Basically to me, its a M16 vs AK debate. The FAL is a bit more finely made, more milled pieces, a bit better accuracy, more bells. But it can also be quite a bit more money. Sure you can get the bare bones FAL parts kits for around $1000, but alot of them are of dubious quality. You are much more likely when buying a FAL to have problems, the you are with a HK91 clone. Lets not even get into the confusing metric vs inch variations of the different FAL clones. You can go buy a HK91 clone and know that its going to work. In the end though they are both great rifles and it comes down to personal preference. I can't say that either of them will do the job better then the other for their respective purpose.
However I am an AK guy (have lots of them) and I generally prefer the HK91 design over the FAL...doesn't mean I won't get both.