MP150 or MP200

I'm pretty sure we are going overboard on the subject of new vs vintage in the context of phono cartridges . There is always a middle ground where we can all be happy .

I remember my first true highend cartridge , a Supex 901+ . It was a high output Moving Coil cartridge which sounded wounderful 
 Even today when you see them being sold at ebay , audiogon or USaudiomart they don't have to wait for long to be sold but they sell for quite a bit of money . And they are vintage . I bought mine at 1979 , cost me 225.00 at that time . Had it connected to the phonostage of a Audionics by Oregon BT2 phonostage and that into a pair of Dynaco Mark 6 mono block power amps .

What I am trying to say is when a piece of equipment is good , it is good , period . Take a well performing pair of Dalquist DQ10 speaker and I'm pretty sure they can stand their ground against any modern speaker design with the latest and greatest computer animated design 

So don't disregard something just because it was design 20 or 30 years ago . Same thing applies to vintage cartridges . I remember Harry Pearson of the Absolute Sound use to say that the midrange of the ADC MM cartridges is the best he has heard in his life . Apply the same to the midrange of the Marantz 8B tube amp

I'm kinda a newbie here but I have the mp-200 and I loved it... until I discovered the world of MC carts.  If you're looking for more detail and refinement, save up and go for a HOMC.  Maybe a Hana S or lower end Dynavector.  I really dug the balanced and warm way the mp-200 presented the music but in terms of detail and realism, there's no contest.  To be fair, the MC cart I got to replace the Nag was around $700 but it was worth it!  On another topic the tracking ability of a Shibata or Microline stylus is way better, especially if you listen to classical music with it's large dynamic shifts.  Of course you can get an MM with said styli but I'd make the jump to a decent MC.

As far as I remember, an MP200 has a boron cantilever, which pushes it up to a much better product classification. It is worth the extra.

I’ve also been using the MP150 for some time and holding for a bit saving up for a new one. My arm is Jelco 750 and phonostage is RCM Sensor 2... was thinking of upgrading to MP500 but would greatly appreciate any recommendations around $1k. Soundsmith Carmen 2 and Hana El also on my list.

* I’m not familiar with Grace but I do know Larry Levan used them at the legendary Paradise Garage with Infinity Black Widow arm, can’t remember the model, a friend told me once, probably would have been a really sturdy cantilever. (I listen to a lot of music from that era).

As I have said previously the mp150 is an excellent cartridge but at present prices not sure it is THAT much better than the mp110, both of which I own and know very well.
The mp200 would likely be the next step up from the mp110 imho if not for the fairly recent price hikes .
As has been established there is a lot of competition at the $500 mark whether you go vintage or new mm/mi or even mc.

Best of luck OP, it is a tough choice at that price range but if you really like the house Nag sound then maybe the mp200 would be the right call.
YMMV