I've played all three at one point or another. I capped a Spellsinger, then switched to Virtuoso after, which is what Mirys is right now.
As said, Bards take a long time to really come into their own, much later than most classes. They lack either the number of songs, the song duration, or the spell points to do much than limited buffing and healing, up until 12 or so. Then past 16, they don't get a whole lot as they haven't got any Tier 3 Prestige Enhancements, they have a short spell list. This is why you see a lot of 14/6, 16/2/2, and other deeper multiclass builds using Bards as a base.
On the other hand, any party/raid leader worth their salt will want a Bard in the group, as they have buffs which stack with everything, other buffs which draw some of the pressure off of the Divine and Arcane of the group, and can hold their own in melee with a decent weapon, using Displacement and some crowd control abilities to mitigate damage. Their main CC ability gets to be very powerful, working often where others do not, and they can boost it further to affect undead and constructs as well.
Warchanter - IMO not worth it right now. They get a small boost to their Inspire Courage, medium armor proficiency with no arcane spell failure, and the ability to use AP to get a martial weapon proficiency (worthless with the spell Master's Touch). Their tier 2 song gives a small bonus to Doublestrike, at the cost to Fortification. Tier 1 song is DR5, which is readily available from other sources. For a melee Bard, the difference in dps in almost non-existent versus the other PrEs.
Spell-Singer - Extra spell points helps the limited SP pool of the Bard, and the PrE songs are highly useful to casters (both the Bard if built as a caster and other DC based casters). The spell point regen song basically gives you unlimited sp until you run out of songs, and that means unlimited CC/Displacement/Haste/Rage/Healing.
Virtuoso - More songs, and enhancements to your song CC. Enthrall is an upgraded version of the basic Bard song CC, and Capering Song is very useful to stop most single targets.
I would go Spell Singer for a first Bard, myself. The extra spell points helps alot when you lack the gear to mitigate the low sp pool, and the regen song is invaluable while you learn to manage that pool. Virtuoso is a decent choice, though you won't see many running around. Most Bards seems to split between Melee Warchanter and Caster Spell Singer.
Mirys can solo Epic Hards without issue, including the HP-inflated Gianthold Epics. She's also stepped foot into Epic Elite pugs, and managed alright, though there are certain design choices in EE's (and even EH's and some EN's) which hurt Bards more than other classes, since they lack either the hp pool or the high PRR to absorb the high damage numbers coming in. This is more a problem with the design of the mobs than the class, they're being designed around Stalwart Defender fighters with 50%+ damage mitigation from AC, 40% from PRR, 20% from Blur, and 1000+ hp. 500+ hp Bards with no PRR and no AC are kinda stuck with only Displacement.