JIM--as JC has said let the fun begin. As you have said most comments will be by what others now use and prefer.
First as a beginner you own one of the finest vises made,USA with a lifetime warranty. Be happy with it for a few years. I own 6 Griffin model 2A's a Odyssey and a 3ARP-the 2A's for kids classes. Your Patriot is made to be used at a 45 but I do use my 3arp horizontally at times tying tube flies. A true rotary is usually only to wrap material on the hook and look at the back side of the fly, that you can do with yours. I have material clips that I never use and your answer for a lghter vise for the fine art of tying--most prefer the weight.
If you cant stay with the vise you have and would like the Mongoose in the future call Griffin at 1 800 344 3150. Ask if they would make up a kit to change over your Patriot to a Mongoose. I bought a kit to change the 3ARP to the Odyssey and found I can use both one with c clamp and he other with the pedestal.

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Bill