True, the 91-30 (full size rifle) is probably more pleasant to shoot.
(I have a Finnish 28-30, but I got it long ago when Mosins were uncommon here, so I got it as an interesting oddity.)
I don't really get the popularity of the Mosin, except they're
A) cheap and
B)available.
Now that's plenty good in my book. A wise man once said,
"When kisses are a shilling each, we should adventure on a few."
Which is another way of saying, "When Mosins are cheap, load up on 'em."
I think they're clunky, myself. Once you try a Lee-Enfield, you'll never be so impressed with a Mosin. The Mosin is no more powerful than a K98 or a Springfield, and either is a better rifle. (That's why sporters like the Winchester 70 are based on the Mauser, not the Mosin.) Blah Blah, yadda yadda.
Mosins are cheap, and available.
What is more, AMMO is cheap and available.
Mosin bolts are fun to disassemble. Sort of like a Chinese puzzle.
Listen, oh Youth: I look back over the years and I KICK myself for not buying more guns when they were cheap and available.
I'm glad I bought every one I did, even that clunky Finnish Mosin.
I profoundly regret selling the ones I sold. (Oh, where is my 03-A3?!)
So why, oh Youth, WHY do you come here and tell us "I'm seriously thinking about buying a..."
Buy it! How can you go wrong? A robust, powerful, clunky rifle for under $100! One that uses readily available cheap ammo!
Hell, boy, buy the whole set! M91! M91-30! Finnish M39!
Gather ye rosebuds while ye may!
Adventure on them kisses.
Anyway, that's my suggestion.