Many aircraft have windscreen bird-strike limits of 250Knots below FL100 or 80, both jet and turboprop. If you have to slow down behind jets, it is not because the Q400 is faster, but that the jet chooses to slow down to 250knots or less due to company sops, atc, etc. Most turboprops can scream in towards an approach because they have better get of of jail cards than a jet for slowing down late. Like it or not, most companies will prefer to familiarise t/prop only pilots in the RS before moving them to LS, with the exception maybe of smaller jets like the EMB145.
Regards.