I have some of both.. The deal is that SLR 104/105 guns and 107 guns are great, they are built tough and accurate. 106 (5.56) guns are a bit funky and don't always run right. I personally find my Saiga based guns to be my favorite. They are 100 series guns , and have all the current technical updates that factory mil guns have. If you are looking for a factory built gun, the SGL series are hard to beat. They have all the correct russian parts and are semi auto imports of the mil versions. They also have updated stock geometry on the side folder variants. If you are looking to do a RD style rifle then start with a base model gun. The SGL and Saiga use the same receivers, trunnions, bolts, carriers and barrels.