A built-in dishwasher is installed directly into your plumbing. So all you need to do is load the dishwasher and press start before each use. It’s usually installed within your cabinets, so there are no gaps around it.
Portable dishwashers need to be manually plumbed into the faucet before each use. They also require a bit more effort between uses.
For example, you can’t leave it running while you’re out of the house. The same applies overnight unless you’re sure you’ll be there to turn off the water supply at the end of the cycle.
Built-in dishwashers also have more fun features, are more durable, and are usually a bit quieter.
Lastly, built-in dishwashers are more spacious than portable ones. However, portable ones are easy to transport, are usually on wheels, and are great for small homes or people on the move a lot.