This question, or one similar, has been asked before... and, I created this forum just to help put the comments in one place, here it is:
https://www.st-owners.com/forums/forumdisplay.php?f=159
Now, to answer your question as it applies too me... someone who went from a GL1800 to an ST1300 and back to a GL1800...
Comfort - off the shelf the Wing wins.. but, with minor adjustments the ST can be very comfortable.
Fun Factor - The ST wins here, and I'll admit it.
Brakes - ST wins hands down.
Lighting - Wing wins w/stock lights.
Mileage per tank - ST wins w/300, Wing is around 200 or slightly over.
Luggage - Wing wins only because the trunk comes with it - add a Givi to an ST and the difference is small. The Wing trunk and saddle bags close and can be oppened with the paddles under the trunk, without needing a key.
Built in accessories - Well, do I actually have to say it (Wing wins w/radio, weather band and intercom - also, front speakers) Not to mention the Cruise Control and Reverse which is a godsend for those shorter people like me.
Engine - the ST is smooth... the Wing is smoother. The Wing has some great all around torque and lots of power - The ST much quicker and passing is a breeze.
Maint - 16k valve check for ST - 32k for Wing. Checking valves on ST requires lots of plastic removal, on Wing the valve covers are exposed. Actually adjusting them is similar as they are both bucket/shim valves.
Aftermarket - Well, it sucks but the ST have barely any aftermarket accessories compared to the warehouses full of Wing stuff... even if 90 percent of it all is chrome and lights...
Passenger comfort - the Wing has a sofa for a backseat however many have complained that the wind buffetting hitting the passenger is not tolerable.
Windshield - Electric for ST, not for Wing - ST Wins!
Gas - Wing wins here - it takes regular unleaded - ST needs premium.
If you are more touring than sport - then the wing will probably be your eventual destination... There's still some sport in the wing and you may realize you can have a lot of fun with it.
Those are my opinions/observations.... they work for me and thats why I've had two wings. Take the comments for what they are worth but make up your own mind and do what works for you in the end.