What most people call raised beds, aren’t really very raised. It would be more accurate to call them edged beds.

What are the advantages of raised beds?

They look very neat. They instantly make a vegetable plot look tidy.
Beds are defined which mean you can see where not to step or walk.
It is an edge to strim to.
When made from different materials they can actually allow you to garden without bending.
It is easy to set out to tackle one raised bed at a time when you’re weeding and you can have a great sense of accomplishment by completely weeding one bed.
You can enrich or sieve soil in a small raised bed to help grow carrots and other root vegetables on stony or poor soil.
You tend only the growing space on your vegetable beds and not the pathed areas.
Pathed areas being more clearly defined means you can deal with these more efficiently by mowing or strimming.
Enrichment of soil takes place only in defined growing areas.
Soil can be better than in the ground as it can be easily amended.
Soil is not walked on which is beneficial for the plant roots and soil structure.
Preparation of raised beds means they may be more weed free.
You can harvest more easily in wet weather as you have paths to stand on whilst you pick crops.
Because of the additional soil enrichment you may be able to crop closer.
Soil should drain better as it is above the ground level. This can help on poor soils.
It can be easier to attach netted covers to raised beds.

Weed suppressant covers can be cut to size and placed in beds at the end of the season.

What are the disadvantages of raised beds?

They require materials (usually wood) to make them, this has a cost.
They take time to make.
Wood rots, especially when it’s in contact with soil.
It is a great place for slugs to hide down the side or as the wood helps keep soil damp and if grass is growing on one side this will trap moisture along the wood too, making it a home for slugs to hide during the day.
They will not last for very long and will need replacing every few years.
Any wood treatment to make them last longer is in contact with the soil which can cause contamination issues.
Preparing area for raised beds needs to be thorough else weeds like couch grass can easily get into the raised bed structure.
Weeds still grow in raised beds.