What are the non-combat benefits of going pure Rogue instead of Rogue/Fighter?

I've been building a Swashbuckler rogue and, wanting to get shield proficiency, I've been researching whether to take the Moderately Armored feat or multiclass into Fighter. And let me tell you, the vast majority of advice I see seems to be for multiclassing to Fighter.

I get why this is on a combat level. Almost every fighter level from 1-5 is better for damage than an equivalent level in Rogue. Fighting styles, action surge, subclass feats, extra attack. So from a combat perspective there's a clear winner.

But what's the opportunity cost for losing Rogue levels? Do you guys think the extra defensive and skill check-focused features help offset the loss of damage? How does it feel playing a pure Rogue vs a Rogue/Fighter in practice?