How many motors should my RC plane have?

I am building a RC plane from scratch and I need to know whether I should use 1 big and expensive motor or two cheap and less powerful motors. Speed and agility is very crucial for me. I would be using a micro-controller to control everything. 3d printing prototyping service
Make a note of following:

1) You'll need extra servo motor for an extra propeller motor. Or, you can use same servo for both but you'll face difficulty in housing this in fuselage. In case only one of the propellers fail then, safe landing will be a big challenge.
2) You'll have to mount the two propellers on the wings for symmetry that means you need to have stronger chassis, which can be an Aluminium rod through your wings. That again increases weight. Remember single propeller on fuselage is always weight efficient for RC planes.
3) Though you can use coupled effect of motors for fancy maneuverability but at the same time it will require better skills on your side.

My seniors from IITK made one such wing mounted twin propeller model but they couldn't make it fly. Hence I would be reluctant trying this. At the same time I'll say its a challenge worth taking for an aeromodeling enthusiast. Do a thrust-weight-cost analysis. If you have sufficient thrust from two motors despite addition of all the above mentioned weight then go for it. 3d printing service in gujarat, vadodara, ahmedabad - sla technology