"Anyway, I'm getting older (48) and less flexible, and thinking about a more forgiving ride."

You must be kidding! There is no way, OP, at 48, you're so much less flexible, in your 48 year-old dotage, that you need a more comfortable ride. Admit it, you just want another bike.

Why consider a Tarmac if you want a more forgiving ride? If you have to upsize a Tarmac to make it feel like a Roubaix, then that's another reason for going for the Roubaix.

That said, I'm 62(how DID that happen!?!) and I have a Roubaix. It's extremely comfortable compared to other bikes I've ridden and/or have, especially for long distance rides. However, I love and ride my other bikes, too.

As I don't race, I decided, when it was time for a new bike, to purchase one that would make me hurt less by the end of a long ride. Yet, don't I want to hurt, at least a little, by the end of a long ride?