I have had the following:

MX-810: Horrible, so horrible in fact they no long make it.

MX-900: My first and was a great remote for its time

MX-880 (3): Great remote. Bought one for my parents as well. Ended up having charging issues and had to buy a "camera" charger and keep swapping the batteries

MX-980: Used this in my HT as I needed the logic to deal with TOADs. Used it for almost 10 years and other than a couple of battery swaps, still going strong.

MX-780: Bought on a whim for my daughter. She loves it.

MX-890 (2): Bought one for the LR TV when one of the 880's got a little wonky. Loved it so much I replaced the 980 in the HT with one of these. Best URC remote I have ever had. The power of the 980 with much better ergonomics.

So my favorite is the 890. I have never had the 990, but given its size is similar to the 980 and I much prefer the feel of the 890 there is no reason for me to try one.