I think we are all a little bias, but looking objectively they each do their own thing.
The venza is a 40mpg, wireless charging, 12 inch center display full 7 inch led dash and a crazy 10in HUD optional. Wireless charging as well. The venza splits the difference between Lexus and Toyota like the Avalon does. It's a sweet ride. And the prices between the two are nearly identical with the venza only having 3 trims and the CX9 having 4.
Now I wanted a Mazda due to always having an econobox (stratus, 2 Saturns, a minivan, and my wife's DD a Volt) so ilthe Mazda was hands down my choice. But if I was looking for amenities and MPG as my top necessities. Boy the Venza ticks those boxes very well. It's not a escape hybrid which looks too normal, and it's not an blazer that is all show and no go.
But it's obvious they cater to completely difference audiences.
It was just my suggestion since he drives a lot. If I drove a lot, especially for work, I would put budget and driving comfort over sporty driving dynamics personally.