SAR-1s were early Romanian imported rifles that remained pretty much factory, but needed US parts. These are pretty good rifles. WASRs are the newer imported guns that were neutered. They had new receivers, the funky stocks, and were single stack magazine only - but they didn't need US parts. Then some Century Arms monkeys dremeled the fuck out of the inside to allow for regular magazines. GP, from what I read, are the newest barrels from our country per ATF decree.
WASRs should not have dimples. SAR-1s will. I think the finish of the WASRs are nicer, but them being monkey dicked isn't appealing to me. I think trigger slap still exists, too. It's easy to fix - just Google. If SAR-1s and WASRs are the same price, I'd go for the SAR-1, it's about as close to the real deal as you can get.