I give Inman the edge here. He may be smaller and 2 years older (19..), but you cant refute his season, which was much better than Guerra's. I like both players for the future but with Guerra's age, he may actually gain velocity in the future. This could be a positive or a negative. If he continues to grow and gain strength he should throw harder but may lose some motor skills, having an even more detrimental effect on accuracy.
Another thing I look into heavily is K/BB and Inman is clearly better in that regard. I definitely do not consider Guerra more advanced because he had a couple of High-A starts while Inman didn't. Inman was clearly able to be promoted but it seems the Brewer's have a plan set, which I consider to be a smart move.
It should be interesting to see how the two players develop, but if I had to bet money on which ends up more successful, I would put it on Inman.