I'll try to explain how I got where I am.
My first putter was a 166, in the starter kit. Didn't really know what I was doing, but it worked ok. I moved up, over time to max weight (175s) I tried a variety of molds, settling on the Magic, and eventually the Voodoo. I liked the heavy weight as it seemed the least affected by the wind and covered up some release errors. I could just throw it at the chains.
But I was leaving longer (30+ ft) putts short, as they would fall off the line. Throwing harder caused me to be more erratic. And I remembered how the 166 would just hold it's line a touch longer. I also found out this 175 actually weighed 177, so that explains the sluggish feel.
I started playing around with lighter weights and carried a 172 for true putter and a 168ish for longer, finesse putts. Then I realized that carrying three weights caused more inconsistency then it helped so I settled on the 170 for all putting. I still drive and approach with a 175.
I like this "lighter" 169-170 weight for these reasons:
-I can get a better wrist snap and therefore accelerate it better
-Slightly better glide for the same spin/speed, staying on lines a bit longer, without fading out
-The Voodoo mold handles moderate wind well, so I can use this lighter weight unless it's really blowing hard. I will use my 175 driving putter in strong headwinds.
-not changiing from heavy to light putters has improved my consistency as I've become very accustomed to one weight, one release, etc.
The 169 was the comprimise between the solid feel of max weight and easy to snap, finesse of lightweight, and allowed me to reduce the number of putters I carried.
That's why I prefer it.