Rega Bias 2 or Clearaudio Concept V2, MM

"Which one gives a fuller soundstage, tight bass that does not smother, cleaner highs without harshness, open mids that allow supporting or back row vocals or instruments to participate, better control of the low mids or upper bass -- the cello, tuba, French horn arena; all that nice stuff. I am not interested in opinions of other cartridges unless they are $300 or less, and easily obtainable."

Given that, I would also consider a HOMC. The high output makes them compatible with MM phono stages.

I don't really like Rega cartridges - they are not very neutral and even my Elyse2 sounded dull and lacking in detail. I own the CA Concept V2MM that came with my CA turntable. It is a very good cartridge. It's only real shortcoming is the very audible bending moment of the long but not very stiff cantilever. It manifests as a slight discontinuity in the upper mids. Not terrible but noticeable in a high resolution system.

Without knowing the rest of your set up I can strongly recommend the following cartridges under $300:

Ortofon OM20 (mm)- nude tip, wide soundstage, nice detail without being clinical. Nice warm balance.

Ortofon 2M Blue (mm) - nude tip, more detail than the OM20. Less warm but tighter, deeper bass. Much better dynamics.

Grado Gold (mi)- Huge soundstage, big warm cartridge with lots of detail but sounds a bit rolled off up top. Actually try any of the Grado Prestige. Choose the Green/Red/Gold over the Black/Blue/Silver.

Audio Technica ATF3III (lomc) - nude tip, lovely affordable, neutral. No nasties and very refined. Does not stand out in one area and not bright up top like some other AT lomc cartridges

AT 440MLa (mm) - giant killer cartridge with great detail, wonderful bass and really involving.

Denon DL110 (HOMC) - another giant killer. Not strictly neutral but so musical and wonderful balance.

Ortofon Quintet Red (LOMC) - this one is just over $300 and very pleasant overall. I own the Blue which is more open and detailed but also over $500.

Anything by Nagaoka - big warm and friendly.

Love the Sumiko Pearl too.Not very detailed but a big sound. Very forgiving.

Each of these can sound good or bad depending on turntable, phono pre, speakers, amps, cabling, room, etc.

I own or have owned tables from most of the usual suspects (Linn, Rega, CA, Pro-ject, Technics, Revolver, Dual, Thorens and others). This list of cartridges should work on a wide range of those table/arm combos.

Nagoka all the way the MP-150 specifically, . Gardo Gold will do what you want
but is bit grainy and rolled off in the top as Banejba said.
I think the Rega 2 is a very natural cartridge like most things Rega. I believe it gets a bad rap for just that reason,folks are used to a "hifi" sound and find a natural acoustic music sound "dull"
But they are hard to align on other tables and you can't replace the stylus which is a deal breaker to me.