Been thinking about this and I can't see the point of having twin bikes. I know you are setting them up with different components but that is not going to affect how they ride by much- You will have two identical bikes- doing the same job on the things they are good at and neither able to do the things that the other is not so good at.

I would prefer to have bikes for different uses- say one for hills and one for speed. I don't have the speed bike but I do have two bikes similarly set up as that is the fit that I like. Two good bikes as well but I do prefer to ride one of them on my normal rides. However- if it is going to be a hilly ride- then the "2nd" bike will be used. I know that they now have different gearing but Even when they had identical gearing- one of those bikes went up hills and the other flew up them. They are different Manufacturers- different Geometry and different materials but as Far as I am concerned- each bike has it own Forte.

The one that goes up hills is also the bike I will use on the longer rides. So why do I like the other one? No Idea but it feels more comfortable and seems to be faster. That is also the bike I use on the rolling hills North of me round the country lanes as it does descend and turn easier than the other.

So if I had two bikes -Which I have- I would prefer them to have different abilities -Which they do- but I would still want each bike to be as good as the other-- Which they are.