I like to run one size up on the tires for not only that fatter look but for actual ride security.
So many times you get caught by surprise with bigger than normal potholes and to me, having more tire helps.
My friend says he likes

the 21 inch narrow stock tires but not me.
I had 21-inch front tires on my 2003 1200 Custom sportster and too many times held my breath on some of those tight turns.
I like the feel and control of the bigger but not too big front tires,
I run 110's on the 19 front.

 

I agree, a wider tire looks cooler and offers a better grip. However, there is a point where it becomes too much.
I had a 2009 Road King with a 180 on the rear and while it did seem to be grippy, I felt like I had to work harder to keep it in place when going around long curves. The bike felt like it wanted to stand back up instead of holding a line and staying "tucked in" like my 2003 Road King that had a 140 rear tire.

 

Wheel and tire look great, now you need more fender to match, good luck.

 

I like the wider tires for better grip. Stock F = 90/90/21 and R = 130/90/16.

Now, 120/70/21 and 180/55/18.

 

A wider tire is normally heavier than a narrower one of the same rim size. This increased weight will be unsprung and also contributes to the gyroscopic effect, the negative handling effects outweigh any appearance gains in my opinion.

Gene

 

Upped the size of the width front 100 to 110, and the rear 160 to 170. Fits good using the HD custom smooth rims.
The weight difference is minimal.
I'm not a speed demon, the confidence and handling to me gives more traction in the twisties.
It also cushions more when you hit an unexpected pothole.
The roads are terrible in New England in the spring.
I ran this same size using Metzeler Marathons for 12 years.
I had sticker shock when I priced new tires, so I'm trying the Shinko tires.
The Shinko rear tire has a wider side bead, but they fit the bike fine.

 

I run Bridgestone T31 110/80-19 on the front and 180/55-18 BS exedra G850 on the rear of my 2000 FXDX. It handles way better than it ever did with the 100-19 and 150-16 in the rear..