I think the 2nd one could be more flexible for storage.

I find the second one more attractive, but it's almost as wide as a dresser.

The second option is your best option if you are hoping to maximize your storage abilities! And yes, we have used buffet pieces as a sideboard or dresser for our client's bedrooms in the past. The main difference you will have with a buffet VS a dresser is that your drawers will not be as deep in a buffet/server. Dressers are typically 28"-30" D where a buffet/server may typically be 14"-19" D.

I have a dining room pice in style of option 2 and it hold a ton of stuff but mine is quite long- so longer than most dressers. If it were more petite then, less storage space. Still if you have the side doors, they hold different size things. Avoid fixed shelves- hope for removable or none, since you can use other ways to create a shelf or stack things.
Now this is if not trying to use it for major clothing storage, but for other household items.