An answer through illustration by corollary.....
Many years ago, back before IBM PC's, or Macs, or Lisa, or Linux, or NetWare or NT, I was looking at buying a computer. My choices were a Tandy CoCo, an Apple IIe, a Commodore VIC-20 or C64, and some funky things I'm sure you've never heard of, stuff like Sinclairs with membrane keys, and "luggable" computers like KayPro and Osborn.
At any rate, I asked my physics teacher what he'd recommend. He said "Buy your software first." If your software runs on a CoCo, then you know what the Tandy is the way to go. If it requires a IIe to run, then you'd best support the Apple community.
So how does that relate to rallying?
What memberships you choose depend on what races you plan to attend. If you're only going to be running at NASA sanctioned gigs, go with NASA. If, like me, you're running the ProRally series, then you need to pay the big bucks for an SCCA membership and license. Or, if you can't get enough rallying unless you travel the states and the world, you can buy both, and more besides, like USAC and FIA.
I'll continue to hold onto my SCCA membership because it gives me a chance to work in the Race Control tower at our local race tracks when I'm not in a car, but perhaps your situation is different.
Just remember, buy your software first.
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[p align=right]John Dillon
John @ WidgetRacing.com
www.WidgetRacing.com