All oils that are 0W-xx are full synthetic since conventional oils can't achieve that viscosity at cold temps. Technically you could use a conventional oil if you wanted to since as Bevo pointed out the manual lists 5w-30 as an alternative to 0w-20, it's entirely up to you. As long as you stick to the weights specified in the manual you should be fine regardless of whether you use full synthetic or conventional. Fully synthetic oils tend to enjoy longer change intervals and with regards to the 0w's better cold weather startup characteristics and fuel economy. For summer time this year I'm going to stick to 0w-20 unless I notice a rougher startup due to the temperature outside, which then I'll switch to 5w-30 full synthetic.
There's no option "better" than full synthetic but not all synthetic oils are the same. You can see full synthetic oils from Mobil1 and Castrol for example, and then start looking at oils from Motul, Royal Purple, etc.