It depends. First, barring adverse room acoustics, I would never run a monitor without a sub. I think monitors indeed can throw a soundstage in a mid-sized room (mine is 24 x 12 x 8.5 feet) as large as any floorstander (visitors to my room routinely report on the 'big sound'). When it comes to really large rooms, probably not.
As for full sound in a mid-sized room, with voices no problem. Monitors can project also bass voices convincingly. Big saxophone? My current monitors cannot do that as well as large floorstanders, we'll see how my upgrade to Reference 3A top-of-line Reflector monitors will fare on this point. The ballsy sound of a tuba? My current system can do that very well. Rock? My current monitor/sub combo can do that very well, especially with the more powerful Octave amps that I auditioned last weekend. Left hand of piano, the same. Ensemble of 20 or so players? No problem. Same with drum emsemble. Large orchestra? More problematic, also here I will see how the Reflector monitors will do. But orchestra is also problematic on the majority of floorstanders, unless you get into top quality territory, then they rule.
Dynamics? If you mean the ability to play screamingly loud, at 110 - 120 dB, then no. if you mean the ability to project dynamic range, from subtle changes to large leaps in volume with impact, up to a level of 95-100 dB, monitor/sub combos can be excellent, and mine is as well. In fact, they can be better in that respect than many floorstanders which just don't have that jump factor. Only very high-quality floorstanders powered by not just powerful but, well, dynamic sounding amplification (not easy to achieve), or horns, are as good or better at dynamics.
And no, bigger is not almost always better. Many audiophiles have too large speakers in too small rooms. You can perhaps make it work properly if you carefully trick out the acoustics of the room, with lots of effort.