I use variable speed less than you think.  Most of the CLC flotilla of sanders lacks the option.  Most of the time, "full military power" is what you need with the consumer-level sanders to make any headway on epoxy.  Weight and power are a lot more important to me on the small sanders.  

The only exception among the sanders in our little review is the 6-amp Festool monster. At the WoodenBoat School they turn them down to about half-power because that's plenty and it keeps the racket down. 

I bought the DeWalt variable speed sander from Home Depot after my trusty Porter Cable sander went to the great dust bin in the sky (lasted about 15 years!).

I'm happy with the DeWalt.  No, you probably won't use the variable speed too often while boat building, but it's nice when you're doing other stuff, like sanding pine boards for a project.

  Jim