The 0450 is not just a better flipper, it's a better fidgetter. The size and weight and how it fits in hand make it easier to manipulate and play with. Again, IMO and for my hand size, etc. I also have a 0452Ti and that thing might flip open better than the 0450 but it's not a better fidgetter. Get what I mean?
The 0609 is a great user knife. Yet if I try to use it to fidget with, I just don't get the satisfaction I do with the 0450. It flips open just fine and I love the rounded flipper tab. One of the things I find myself doing with it is putting the middle joint of my index finger on the flipper tab and hold the blade with my thumb and just rock the blade back and forth. But what it's really good at is being used as a knife and cutting things. It's slimmer than most ZT's, not just in blade thickness but handle thickness, too. Fits easily in pockets and doesn't pull on clothing since it's 3.6 oz. And it's 20CV blade stays sharper longer than S35VN. I'm a plumbing contractor so I use it for construction related things but I also work on my hobby car and and boat and it does cutting tasks just fine there too. I don't venture into the woods so I can't comment on how it performs there.
So I guess it all depends what you need most right now: a toy or a user? Again, all IMO.