Hi Bill,
What makes you think the vmsize is pre-determined or determined at all in Azure Host? I don't think it is and am pretty sure I was using small instances in my testing. I think that is something controlled by your Azure account. I'm pretty sure my account only has small instances available because it was one of those free trial deals but I ran past the free time period.
However, whether a small instance really has enough resources (ie available memory) to run it well is another question. If memory is too low it will cause constant recycling of the app pool just like in any other low memory hosting environment and that will kill performance.
Best,
Joe