Both will probably start in the minors. Not being cynical, just that with the # of arms the Jays have in the pen without options, unless Pearson looks like he's Edwin Diaz, he probably starts his season in Buffalo unless there's an injury or two in the pen prior to the season starting. Tiedemann has exactly 11 innings pitched as AA and 78 in his 1 pro season of the minors. He would be definitely limited on innings this season (like.. 130 maybe?) so it's probably better for him to start out in AA to have his innings managed, and if there came a point where he was just utterly dominant and the Jays had a need down the stretch in the thick of a playoff race.. then maybe you bring him up to finish up his innings while helping the club.
I don't see many scenarios where he starts the season out of the rotation with the big club.
*rain....parade*