Does giving an easily-understood talk make the audience think you did something simple?
I will tell you what I've observed in Math.  Similar to what Jordan Ellenberg says in How not to be wrong, one can think of depth and technicality as two orthogonal axes, so one has 4 rough categories of results:


Deep and simple (technically easy)
Deep and hard/technical
Shallow and simple
Shallow (unimportant) and technical


Some people like things that are more technical and some people like things are simple, but deep.  For instance, Atle Selberg thought that the most profound ideas in math are simple and said all of his ideas were simple ones.

Correspondingly some people are more easily impressed by technical talks and some people are more easily impressed by simple talks.  So my answer to:


  Do people walk out of the talk thinking Alice must've done something simple while Bob did something profound?


would be, while it of course depends on the audience, I think this depends largely on the talk.  If you can explain a simple idea that lets you solve long-standing open problems, I think most people will agree this is deep.  However if your talk doesn't make it clear you're solving long-standing open problems, then people will be unsure.  And you certainly want to avoid giving a talk that is shallow and simple, as no one will be impressed.

I myself generally prefer (giving and listening to) understandable talks, and here are a couple other pieces of advice:


Even if you don't want to present technicalities, make it clear to the audience that technicalities are present, and maybe make a few comments to the experts as to how you handle them.
What may seem simple to you, who have been thinking about these things for months or years, may not seem simple to others.  I've many times given talks and worried that it was too simple for the experts in the audience, and found out later that many of them didn't completely understand what I said beyond the introductory material.