[Cmely]

Hey that's cheating. That wasn't on the list of options.

Yes I know. You can't even imagine how I feel bad about that

[Nicolas06]

If noise is important for you, please understand you should go toward a K1. K5 vs K3 is subtle difference for noise. K1 bring 2EV difference in practice meaning you 3200 iso shoot on K1 will look like 800 iso shoot on your K5-IIs. That going to drastically improve your events/portrait/weddings shoots as long as you don't fully control light. It would also ease your lighting equipement job as mixing ambiant light + flash light is often quite interresting in this kind of situations. The problem is that if you buy K1 as second camera, you'll never want to use that K5 again seeing the actual difference it make to your pictures(*).

Back to K5-II, K3 and K3-II:
Overall K3 and K3-II are the same. Very small difference. I would go K3-II if the price is right for the small improvements (bit better SR, KAF4 support, supposedly bit better AF).

K5 vs K3 famillies is quite different. The NR difference is the less significant of theses differences. K3 and K3-II have much, much better AF, improve on metering accuracy and is more pro oriented with 200K actuations instead of 100K and 2SD card support for backup and drastically reducing likelyness of lossing one work due to a faulty card. There also a faster processor.

In the field, for events and weddings and portraits, you'll notice more accurate AF, and of center point being actually being precise enough so that you don't need MF anymore to get an accurate focus on the eyes. At time you'l find the white balance and metering more accurate. Overall the K3 and K3-II will feel faster. Faster to AF, faster to shoot, more FPS and faster to process JPEGs.


(*). I don't think FF is relevant to everybody or even to most. But it all about what you shoot. Events and wedding are exactly the kind of shooting that benefit a lot of an FF modern body with fast modern zooms.