Lighter in what way? I don't necessarily disagree but when I think putty i think:
No tabs and No panes so you're limited to using the OS window manager, and if you want to achieve multiple usable sessions at once you're going to have to arrange and resize these windows yourself or you'll have to use another 3rd party app.
No integrated private key authentication. You have to use like 3 GUI screens (wha?!?!?) to set this up and then you have to run a 3rd party app like pageant.
I had many other gripes before I switched (to a mac in my case) but I can't remember them anymore.
