Hi jimspov,
Your post is well received as you are in the "learning mode". This is always good!
I have the Beatles mono box and many others. I've been trying to ad to my mono collection and have a mono cart.
Here's what I've found out through my own investing in mono recordings over the past 2/3 years.
Since I listen mostly to rock... the early rock recordings that were initially recorded in mono, do sound the best reproduced in mono. Although you can have a good experience through a stereo cartridge, the absolutely best way is in mono with vinyl.
I was surprised early on, how dimensional mono records sound even when through a stereo cart. This just improves with a mono cart. Your question "Is there a greater sense of realism?" is a great one! My answer is yes!
In the end, I think it all depends on how much "the best" reproduction of the music in your own home actually means to you. Then, it IS worth the investment.
Cheers!