MP150 or MP200

You MP110 is entry level model with bonded elliptical diamond and aluminum cantilever.

Higher model like MP200 comes with NUDE (not bonded) diamond and Boron cantilever. One of the reason the price is much higher. 

Never use youtube as reference in cartridge comparison tests. 

As you said you want to stay with Nagaoka, so you could investigate which compatible stylus you could buy instead of a new cartridge. If you have cash for MP200 go for it. 

In my opinion you can easily find a better high compliance MM cartridge like SONY XL50 with Boron Pipe cantilever, but you want to stay with Nagaoka. 

$500-700 for a great MM cartridge is fair price. 

The MP-150 and the MP-200 share cartridge types.
Not saying it’s the way to go unless you are trying to keep spending increments low, but I bought the 150 for about $347 and a year or so later, picked up the JN-P200 (MP-200 replacement stylus) for $169 from a eBay Nagaoka dealer in Japan.
The MP-200 cartridge can be had for around $450-$500... so yes I paid a little more, but not much.
Note that the MP-500 Stylus is not compatible with the MP-150 or 200 cartridge, so the incremental upgrading stops with the 200. The JN-P200 stylus is not compatible with the MP-110 cartidge either.
I liked the MP-150 a lot and did notice an obvious improvement with JN-P200 stylus on my (budget system in this neighborhood) system. Better detail in percussion, brushes, stringed instrument fingerings, etc. Bass tightened up slightly... a little less "boom" and better detail as well.
My (phono) system: Technics SL-1610, Pro-ject Tube Box S2 phono stage, Emotiva pre-amp, Morrow interconnects and ZuAudio Libtec speaker cables feeding Magnepan 1.6 speakers.
I enjoyed making and hearing improvements and now I have a 1 year old, spare MP-150 stylus in case I do the unthinkable and damage the somewhat more delicate boron cantelever on the JN-P200 stylus.

I would go with the MP-200 with the boron cantilever and elliptical stylus over the MP-150.   I purchased one a couple months ago to replace a Grado that came with my new VPI Cliffwood TT and LOVED it. Great balance across the spectrum. Then I came upon some unexpected cash that enabled me to upgrade to the MP-500 which has upgraded electronics and line contact stylus. If you are definitely interested in the MP-200, contact me and I will give you a really good deal.

Chakster, whether the Sony or the Nagaoka cartridge would be better would depend on the tonearm. For medium to high mass arms the Nagaoka would be the better choice. If you had a really light arm then perhaps the Sony might be better. The Nagaoka has many fine reviews. I have not seen one on the Sony.

Sony XL-50 on its dedicated headshell is much better cartridge than Nagaoka MP-200.
It is one of those cartridges that can be found today for reasonable price.
If you have not seen a review for Sony I am not surprised, the XL-50 and XL-70 were the best MM cartridges Sony Sound Tec Corp. ever made (in the 80’s). At that time SONY was pretty serious about analog (cartridges, turntables, tonearms).

SONY established Sony Sound Tec Corporation to produce phono cartridges. Not every equipment manufacturer can make a phono cartridge, but the Sony Sound Tec Corp. combining all the passion and knowledge has released some very interesting models in the early 80’s. The XL-50 is one of two finest Moving Magnet cartridges from SONY. Very special features are as follows: The Joint-less delta-type core; Boron Pipe cantilever and nude Super Elliptical Diamond; A screw holds the stylus holder firmly in place; Distortion caused by flex is virtually eliminated; Cup-shaped damper and tension wire! This lightweight and high compliance cartridge is designed for low mass tonearms. Loading recommended by the manufacturer is from 47k Ohm to 100k Ohm. Cartridge output is 2.0 mV. Frequency response is pretty wide: 10Hz - 50000Hz! The price for XL-50 was ¥25000 in 1981. Boron Pipe cantilever is nothing but a grown crystal of Pure Boron into a pipe configuration (wow). A tip mounting hole made using a laser beam. This technology is no longer available, instead of ultra lightweight PIPE configuration you can get only heavier Boron ROD configuration from cantilever manufacturers nowadays. Boron PIPE is associated ONLY with vintage High-End cartridges (MM or MC). I have two samples of SONY XL-50 and this is an excellent MM cartridge with exotic cantilever!

Nagaoka branded Jeweltone in Japan and all new models are just a versions of the very old design from the 70’s. Jeweltone MP-50 is Nagaoka MP-500. An old Jeweltone/Nagaoka MP-20 is new Nagaoka MP-200. Nothing new here @mijostyn