I agree that in 5e they are the most fun solo class. With college of valor or swords you can do similar damage per round to a ranger, heal as well as most classes, and have half proficiency bonus on all skill checks.
Most powerful could mean alot of things tho. Damage per round would probably go to fighter, Nova damage from a crit would probably go to paladin, tankyness would go to barbarian; etc, etc.
It depends on the DM. If the DM permits the Bard to influence folks well enough, he can hire a party without spending money and if things don't go too well he can slink away and try again. But if your Bard doesn't have a chance to influence folks (extra NPCs) to join the party and the dungeon is pretty much hack and slash then he'll play a supporting role. It could also depend on the width of the dungeon passage compared to the number of players (and tanks) in the party. It may be just plain wise not to have him drawing his sword. But, in my opinion, outside combat, especially in town, the Bard is the bomb!
I've just started out in D&D in the past few months. I was immediately engrossed in it and have spent much of my time researching and exploring the role playing possibilities. Bards not only fit how I like to play and imagine storytelling, they just seem endlessly talented depending on where you want to take them.
It seems depending on your party play and DM, a Glamour Bard can pretty much own a town and run social situations for infinite possibilities and surprising, dominating power. My first party, full of two other new players and a first time DM I could tell they might not know how to handle the complexities of such a Bard in social situations, plus we needed a little more support on the front lines with battle, which I could tell is what everyone wanted to do mostly anyway this first experience. So I opted for a crafty College of Valor Bard. But as we develop, I plan to make a charismatic, powerful Glamour Bard. Seems like the power of social influence can really excite some amazing game play experiences.