Basketball is a team game, and you play with 4 (your team)+ 4 (other team) other guys, in defence and offence. I mean that the things that you do 1 vs 1 in a try out are not the same things that you do in a game 5 vs 5. Rubio is a great, great passer and you will never see this in a 1 vs 1, where perhaps Jennings can beat Rubio. And more than this Rubio seems to have the ability to improve the game of his teammates.
I am from Italy so i saw playing Jennings on TV and read about him and Rubio on newspapers, and while Rubio is a starter in his team and considered the best young player in Europe (and one of the best overall), Jennings simply stinks, playing limited minutes always from the bench. Mentally i see him like the first Marbury, great ego, perhaps good numbers but not a player for a winning team.