If anything Losman is closer to Clausen than Gabbert. I am not saying that because of I like Gabbert more than both of the others, I am just saying that losman and clausen have similar height and weight as well as arm strength.
Interestingly they both struggled under pressure as well in college. In 2009 Clausen was 66% overall in completions but he dropped to 52% on third down. Likewise Gabbert was at 63% for the year and 44% on third down. Clausen continued to do so in the pros. Frankly I think Gabbert might struggle in the pros as well. One of the biggest positive for Newton was that under pressure his completion percentage went up not down. Overall on third down he was at 58% versus 66% overall which was not a big drop off. When blitzed by 5 guys or more it went up to 76%.
Maybe it is me but I saw enough 3rd down blitzes which turned into sacks or throw aways to last several years. Unfortunately picking Gabbert might very well end up being more of the same. More of a feeling than anything I can prove one way or the other.