but being a customer of a factory team is always going to be worse than being THE factory team which you havent allowed for.
Unquestionably the Merc engine will be restricted some how for customers, so only Merc have the best engine, McLaren, Williams and FI will be at least one notch below that.
Ferrai as an engine may be worse off from the pure engine point of view but I would put a heavy bet on the fact they are able to rely on 100% of it developement wise unlike customer teams.
2ndly we have no idea if /how McLaren have already designed their chassis with Honda in mind (baring in mind how long they have known about this , designing the chassis around the Merc for a single year where they are most likely to trail Marc anyway would have been a bad move)
Maybe look at ALL the evidence not just cherry pick some evidence