A couple months ago I decided I wanted to get a Sage. 4 was out of the question, just not my style. 2 is a great option but was a little more pricey. 3 was tempting but if you watch videos or look at pics you'll see its considerably more 'blocky' than the 1. I'm a sucker for carbon fiber so I ended up getting a used Sage 1 on the exchange for $80.
I can't speak highly enough of this knife. I know some people highly dislike liner locks but I'm a big fan. They're strong enough for my tasks and are just easy to operate, specifically with only one hand. The Sage 1 fits my hand perfectly and I wear size large gloves.
I used to own a large grip and it's a great knife, and although I miss the axis lock, I MUCH prefer the carbon fiber and the overall fit of the Sage 1 compared to the grip.
If you like liner locks I'd say get a Sage 1 now! If not, I can't speak on the Sage 3, but I would recommend the 551 Griptilian as I owned one and it was a great knife.