Besides being swivel armed, is the red patch on the figures different? Are all the swivel arm red patches like this? Let me know as I just noticed this. :)

http://members.aol.com/hollyanddave69/flash001.jpg

Thanks,
Dave

Yes, they are all like that. (untextured) :)

Yep, Short-Fuse is right. There are subtle variations in the arms of the straights versus swivels. I'm sure you also noticed the difference in the waistpieces, too.

The bicep pockets moved from the side to the front on the swivel arm figures with long sleeves.

Both Flash and Grand Slam have the texture differences. Also, it appears to me that the Swivel arms have slightly larger gloves.