I've never played FE Gaiden, but I honestly wasn't a big fan of Shadow Dragon so I'm not sure I'd like this one either. SD was too faithful of a remake, I'd rather they'd have added more character stuff and redid some gameplay stuff like maybe adding Lord/Thief promotes and making it so that Marth isn't the only one able to visit villages.
I did appreciate some things about Shadow Dragon though. It introduced reclassing of course, and I actually rather liked the unrestricted nature of it in SD. Hard 5 is ridiculous but I actually prefer something like that over Maniac mode where everything has Vantage+ and such.
You don't have to worry about only Lords being able to visit Villages, since while that's still totally the case, Villages are entirely separate locations from Battlefields and thus doesn't require hauling Alm's or Celica's asses halfway across the map. Battlefields also contain no chests, locked doors or drawbridges and this game predates the Dancer class so nobody goes without at least one promotion unless they're already at their top class.
Also reclassing in New Mystery was less restrictive than Shadow Dragon's since a second playthrough unlocked the full reclass set (save Pegasus/Falcon Knights) for males (and females gained access to the General class to accommodate Sheema; though they were still denied Mercenary/Hero classes in spite of Malice's inclusion, she just got reclassed into a Myrmidon which is kinda ironic given how Narrave, the original Myrmidon archetype, was a Mercenary until the SD remake reclassed him into it; of course the reason why something like a Myrmidon class wasn't in the original was partly due to the dodge formula not being refined enough to support dodge heavy classes; and yet it gave us Clerics/Priests who could only level up through taking an axe to their face).
Plus they can't screw up stat caps as badly as they did in SD. So many Prepromotes became bench/gaiden fodder since their terrible growths weren't also adjusted to fill in the additional +4~10 points (unless your names were Sedgar or Wolf). (Unless they nerf the Angel Ring like they did with New Mystery's Star Orb Shards, which would make Gaiden's 40 caps unobtainable for every non-Villager/Mercenary/Hero character.)
That said, don't expect any high Resistance scores either (as nothing short of promotion gains actually influences them, and that includes character and class growth rates which topped out at a combined total of 0%).