What’s the advantage or disadvantage of using a mic that plugs directly into the USB port for recording dialogue … as opposed to a mic which is also connected to a mixer

USB microphones can be useful if you only need one microphone and you are on a tight budget, otherwise an XLR microphone with a suitable mixing desk or microphone pre-amp is likely to be better.

Does your mixer have a USB output?

A USB mic is more convenient.

Some “podcast mics” have built-in headphone jacks for zero-latency monitoring. (Some audio interfaces also have zero-latency monitoring, and of course you can get that with a mixer too.)

You can only use one USB mic at a time.

Some USB mics are prone to picking-up noise from the USB power. (This can also happen with USB-powered interfaces).

Some USB mics don’t have a recording-level control.

Stage/studio mics won’t interface correctly with a laptop or regular soundcard. You need a mixer or audio interface with a balanced (3-wire) connection, and an audio interface or mixer can provide phantom power for studio condenser mics.

Thanx, Doug. I currently use a mixer and the only recordings I do are book narratives. I seem to have a lot of problems with the mixer (too many knobs and dials which can easily get out of whack).

I willing to purchase a good mic, use the USB connection and jettison the mixer if you think that will provide a quality sound track … and, if so, any recommendations???

Blue Yeti or Shure MV5 The 3 Best USB Microphones of 2023 | Reviews by Wirecutter

yeti NANO or Rode NT-USB Mini is probably good too.

Just make sure you get Zero-Latency Headphone Monitoring.

You could use a portable recorder like a Zoom H1n or H2n to connect to a PC as well but that would add extra steps and since you seem to desire simplicity, I advise against it.

Most USB mics seem to be condenser models as opposed to dynamic. Is there a meaningful difference … I now use a dynamic mic

The Benefits of Condenser Mics
High sensitivity leading to high fidelity sound recording.
High sensitivity means good response at high frequencies.
Ideal for use in recording vocals, either singing or spoken.
Unlike dynamic mics, the electronics mean that these mics are available in many different form factors, from large mics to small lapel mics.
The Drawbacks of Condenser Mics
The requirement of phantom power.
Typically higher cost due to electronic parts.
The electronics and capacitor are somewhat fragile, meaning they can be easily damaged.
High sensitivity leads to poor performance, or even distortion, in environments that aren’t quiet and echo-proof.

The Benefits of Dynamic Mics
Relatively inexpensive due to low cost of internal mechanisms.
Durable and rugged.
Ideal for recording louder sounds and instrumentation, such as drums or amplified guitar.
Low sensitivity means they are unable to pick up distant sounds, making them better suited for live environments and minimizing feedback.
The Drawbacks of Dynamic Mics
Flatter recording range leading to flatter audio.
Low sensitivity, especially at high frequencies.
Low sensitivity leads to poor performance in capturing detail in sounds.
Poor transient (high amplitude, short-duration sound) response.

From https://www.makeuseof.com/tag/condenser-vs-dynamic-mic-actually-need/

@yogada8498 It would be better if you answered questions from your experience rather than just quoting from articles found on the Internet.
Most of the points in your previous post are either incorrect, or require qualification. For example “sensitivity” does not necessarily equate to “fidelity” - it’s quite possible for a microphone to be both sensitive and poor sound quality, or low sensitivity and high sound quality. Similarly “High sensitivity” does not mean “good response at high frequencies” - sensitivity and frequency response are different things and not necessarily related.