I started on alto and after a year or so got a tenor, and instantly thought this is the one. Although the right mouthpiece issues raised its head... Finally after testing a few in a shop I settled on one, learnt to hate it, bought the one I always though I should get, then someone introduced a PPT, got that, then made a daft ebay purchase - "make me an offer" which I did, sold the first two and now finally appreciating that any deficiencies are mine and sticking with what I've got until I start making a good sound. All set, I am a tenor man...
Recently I've been through a bit of an extended blip on the old motivation level and needed to kick myself back into practicing. At about this time a chance curiosity in the yard sale area resulted in me getting a new alto mouthpiece and I decided to focus on that for the time being. I've always found the Alto a bit of a challenge tonewise, never being able to pitch it right, wanting it to be full sounding with clarity, instead I tend to be either stuffy or grating!
So now I'm back on the alto and loving it, it's faster, sharper, a little more forward and pushing me all the time as the tone quickly suffers if I loose focus. All set then, I am an alto man...
If only it were so easy, in essence I like to think of myself as on the journey to being a saxophone player and will always want to keep an alto and tenor close at hand, I don't think I'm naturally inclined to either, as I have to work hard with either one.
The biggest deciding part is often dictated by what I've just listened to, for example if I listen to Wilton Felder's solo in this:
http://www.youtube.com/watch?v=iMI3INBzVIA
Want to pick up my tenor and yet if I watch David Sanborn in this:
http://www.youtube.com/watch?v=EYnF2eDIuHI
I want to pick up my alto, it's not the best example of a Sanborn solo, but the smile that he shares with Mr. Clapton at the end of his solo says a huge amount.
So after all that I think I will probably just go back and forth between the alto and tenor as my mood and desires change. I don't think one being easier than the other is necessarily a deciding point. Before the sax I played guitars and if you take two classics, the Gibson Les Paul and and Fender Strat, both are exceptional instruments that have stood the test of time. The Les Paul is easier to play than the Strat, the Strat is just a little more awkward, you need to fight it a bit, and that is part of the personally of the instrument, it's needed for it to be what it is, just like the alto and the tenor.