That's very debatable and you said it right there, Trouba will get a big contract so that right there makes his value lower than Larsson's since Larsson is signed to a steal of a long term contract so stating that the price for Trouba's RFA rights is to the level of Hall+ is laughable.
You may not like it since you paid such a high price to get Larsson, but it's not debatable. Trouba is better.
A big contract does not make him less valuable. If we decided to trade him, teams will ALWAYS pay for quality.