Bambino Plus ($400-500) if you already own a good grinder or plan to buy one separately. Barista Express ($600-700) if you want one machine that does everything and don't mind the grinder being "good enough" rather than great.
The Barista Express: All-in-One Convenience
Built-in conical burr grinder, 54mm portafilter, PID temperature control, manual steam wand. It grinds, doses, tamps (with the included razor tool), and pulls the shot. One machine, one counter space footprint.
The grinder is the trade-off. It's fine for most people - about 30 usable steps for espresso. But it's not as consistent as a standalone grinder in the same price range (like a Baratza Sette 270 or Eureka Mignon). If you're chasing latte art competitions, you'll outgrow the built-in grinder. If you want a solid daily espresso without fussing, it's more than adequate.
The Bambino Plus: Better Shots, No Grinder
Same Breville thermocoil heating system, same 54mm portafilter, but with a 3-second heat-up time (the Express takes 30+ seconds). Automatic steam wand that textures milk to the right temperature without guesswork. No grinder.
The faster heat-up matters more than you'd think. When you want espresso at 6:30 AM, waiting 30 seconds vs 3 seconds feels like a big gap. The auto steam wand is also genuinely good - it produces cafe-quality microfoam for flat whites and lattes consistently. The Express has a manual wand, which is more capable in skilled hands but takes weeks of practice to get right.
The Real Decision
Already own a grinder (Baratza Encore, 1Zpresso JX-Pro, anything decent): Get the Bambino Plus. You'll save $200 and pull better shots because your standalone grinder is almost certainly more consistent than the Express's built-in one.
Don't own a grinder and don't want two machines: Get the Barista Express. The convenience of one machine is real, and the grinder is good enough for daily use.
On a tight budget: Bambino Plus ($400) + a hand grinder like the 1Zpresso JX-Pro ($160) = $560 total. Better shots than the Barista Express for $40-140 less. The catch is hand grinding takes 30-40 seconds per dose, which some people hate.
One thing both share: Breville's 2-year warranty and decent parts availability. They're both machines you can maintain and repair for years.