Logitech M505 vs. B605: Which one should I get?

Which one's actually better? Anyone have experience with these?
I've been scouring Google, but I can't seem to find anything useful...
I'm planning on picking one up tomorrow, so if you could get back to me soon, I'd appreciate it.
thx!

Just picked up a 505 (non-dash version).
It could probably use a lock...

So, what are we thinking? Any initial impressions? 👍

So, after the first 24 hours of heavy use, I haven't run into a single bit of lag—zero issues across the board. Honestly, I’ve never worked with a better wireless mouse, not even those high-end models that cost way more than $100.
Some people might find the three-button layout limiting, but for me, it’s actually a plus since that’s exactly what I was looking for.
I have pretty large hands, and while the M505 isn't massive, it’s incredibly ergonomic and fits my grip perfectly...🙂
I actually appreciate the weight (with two AAs inside), but the real standout is how accurately it tracks on just about any surface I've thrown it at—desks, glass, mirrors, crumpled paper, even my bed...😁