Differences between VPI Prime and Aries 2

I currently have an older VPI Aries 2 turntable with the acrylic platter.  I'm considering trading it in / trading up to a VPI Prime turntable.  The longer I look - the fewer differences I'm seeing.  Both tables can use or come with the JMW tone arm.  The motors are more or less the same too.  I plan to keep my Ortofon 2M black cartridge and use it in a new deck. 

I'm not seeing huge differences to justify the "upgrade" cost.  What am I missing?
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I'd keep the Aries and see about upgrading the platter to a Classic / Prime platter or an Avenger platter.  Might need some spacers under the arm and maybe a SDS (or similar) to adjust the platter speed.
The primary differences are the aluminum platter, a $1000 upgrade to Aries, and the 3-D printed arm, $1800 (10" arm)  upgrade to Aries.  If you want to do either of those two upgrades then it may be worth it to go with the Prime.  Now if you have the extended Aries which uses the 12" arm then you can't make a direct comparison since the 12" arm will not fit on the Prime, at least without looking very odd.  

Thanks for the comparison pmotz - that's the information I was looking for.  I didn't realize the 3D tone arm & aluminum platter were that pricey - that puts things in perspective.

I've also learned that VPI's optional (~$1k) periphery "outer ring" clamp only works with the aluminum platter.  It will not fit the acrylic platter on the Aries.   

You are asking a good question. I have a VPI Aries 2 Black Knight, but I've switched to the 10.5i Classic 3 tonearm, and it looks fine IMO.  The VPI 12 inch arm would look sort of odd to some in a rig like mine, given the proportions of the Aries standard (not extended).  I noticed an improvement with the 10.5i arm in terms of detail and soundstage, but also with bass response. Also am using the SDS speed controller, which I consider essential.  If I could find a VPI heavy platter, I might try that as well one of these days.

The Prime looks very nice, though, with its updated styling, and it might be the sweet spot in the VPI line-up. 
T-bon3, the periphery ring will work with the acrylic platter if you have the platter with the rabbet (or notch) in the top outer edge.  I have an Aires Extended with acrylic platter and periphery ring.  To me the periphery ring is mandatory, but is expensive and an option on most or all VPI tables.  The best deal with the Prime is the 3-D arm, if bought separately it would cost more than half the table.  The price I quoted ($1800) is just the arm, the base is extra.  The SDS is another worthy addition, but it to is generally an optional item, i.e., not included in the price of the table.  The nice thing about this site is you can find many of these upgrades at a good price.
I have an Aries 2, very satisfied, with it's great sound.  My unit has the 'black aluminum' platter.  I also run it on the SDS and have a periphery ring from TT weights in Canada, which fits and was a fraction of the VPI unit. I have always sought the extended platform so I could use two arms, one dedicated to a mono cartridge.  That for me would be a worth while upgrade.  Still looking.  The Prime table, which I have heard at  local dealer, did not impress me.  I could not get the dealer to let me have it for a trial in my system, so I will pass.  I am sure all know that Harry is a marketing genius, given he is constantly reinventing the 'wheel' for great profit. Don't get me wrong, VPI makes great products, but they are not great values, especially if you engage in the upgrade path. So, if you want to move on to Prime, sell your current VPI and purchase. Also, there is a lesson in the acrylic platter, which was considered to be an upgrade and turned out to be nothing like that.  So, upgrade sometimes does not get you there.