Yeah tier 1 does have it's advantages over tier 2, but it really depends what you are comfortable with. I personally like the ability to test on my netbook, pc and android all in one fell swoop. If I had bada, iphone and such it would be even more useful.
If you can use both, as you say, I would do just that, and use both. Anything that is just a simple (or relatively so) game you can knock up easily in tier 1. If you are planning to do something a little different, that could perhaps take advantage of a particular phone specific function, then tier 2 is the way to go.