You will be shocked how much difference fairing can make but not every bike with fairing is brilliant!
For example I have always ridden sports bikes up until 8 years ago. The fairing on sports bikes was good but to keep everything off you had to be tucked right in with your head down! if you sat up a little then the screen directed the air straight to your chest or with a double bubble screen straight to your head. My hands always suffered in cold weather as there was no protection at all.
The FJR with electric adjustable screen was better and with a larger screen speeds of 90+ with the visor wide open proved the fairing and screen did a great job and kept most of the wind off. The mirrors are designed in such a way that it deflected the wind off your hands but you could still feel the cold! Heated grips helped
The R1200rt on the other hand is like being in a car coldest I have seen is 3°c out and heated grips on setting 3 with summer gloves and my hands where still melting the heated seats made a great difference too but the fairing is great at deflecting the air flow
coming from naked you will see a big difference in the smallest of fairing and I would recommend hand guards for winter