Lambda Defence with SD kit, Marayama and Archwick GBB's. On Vorsk 6 gas and using .2g BB's we get 340 FPS on the Lambda, 320 on the Archwick and 315 on the Marayama. The Lambda is the softest shooting and could do with some beefier bolt return springs and it's a bit underwhelming to fire. If you are after quality and performance then get the Archwick as it's outstanding. I tried it with 0.3g's and it had no issues lifting them and the hop still had more life in it and I think it probably could do 0.36g BB's out the box.
If the straight mag version is what you want, but on a budget, them Marayama are (or already have) releasing a straight mag version with the spare mags around £25 overseas which is about 1/2 the price of the Archwick mags but sadly I doubt they will be compatible between GBB's.
Oh and the Lambda magwell is annoying as VFC and Raven mags can move forwards and backwards, sometimes releasing a little gas, which is a bit annoying. Some sticky backed foam inside the magwell will sort it.