I hate to say it, but because of sheer utility I'd probably keep the 3-speed first gen IRO Mark V. I love, LOVE my other bikes, but the 3-speed IRO is so much more practical for everything, like going to the store, riding in the rain, putting bigger tires and riding in the dirt, fenders, racks, trailers, etc. Plus, it's like the indestructible bike, hit by a toyota tundra and the thing is still straight as the day I got it.
If I didn't have to worry about anything like utility, I'd ditch everything and keep the new bike, it is perfection by way of steel and carbon-fiber.