I went from a ST 1300 to my '13 DL 650. Suzi is noisier, vibrates more, has less wind/weather protection, and has more wind buffeting. It also has a surprisingly comfortable seat*, is lighter, more maneuverable, lighter, easier to park, lighter, and more economical on gas, and lighter. I've spent a lot of money trying to remedy the noise/buffeting issue and put on the DL what I had added to the ST, with only partial success. I am, however, getting there, and realize that there are always tradeoffs. Nothing that the ST did well quite makes up for its weight when stopped, and while it made the miles disappear and erased the difference between 65 and 85 mph, I like the Suzi for exactly what it is.
They say you can never go home. I'd suggest you read a lot more threads here and start modifying your new bike. Don't look back.
*Sargent - it came on the bike. Oh, and the DL has way more storage in the side and top cases than my ST.