Neither, inherently. You could say that monitors (the smaller ones with limited bass output) are possibly less likely to run into standing wave problems, but that would probably simply be due mainly to the comparative reduction of bass energy in the same room.
But, generally, bass problems have different causes and solutions than reverb and echo. In part that may have more to do with the fact that, to our ears, sound becomes basically more directional as frequency rises. When you start getting up into the midrange you're getting into the area of noticeably increased dispersion. Dispersion is usually greatest with Omni-directional types (some Walsh, Atmosphere...). Next, in order of decreasing dispersion, would likely come the dipoles. Then may come standard, box monopoles that use conventional cone or dome drivers. If their crossovers are up to par, they usually have rather wide dispersion in the room, those with narrow front baffles may be thought of as having the widest among them. Those monopoles that use non-standard drivers (like ribbon tweeters or midranges, for example) may have noticeably less wide dispersion than with conventional drivers, though. Last, I suppose, would be the speakers that have been specially engineered by the maker to be narrow dispersion speakers, or may have a specially designed apparatus attached to the baffle that is meant to accomplished this task. That would be speakers like those from Emerald Physics, Wavetouch, VMPS or any other design that uses an array of horns or waveguides, etc for that purpose.
Lots of manufacturers will give you the spiel about how restricting the width of the dispersion in the room will greatly reduce the effect of interactions. IME, a well designed conventional monopole can have (in a good system) a "true, 3D, walk-thru soundstage" as you may have read of before. The restricted dispersion designs can have just as great a soundstage at the LP, it's just that if you move much off axis, or stand up and walk around, the stage collapses.
Otherwise, what is said about the advantages of restricted dispersion designs I believe is pretty much true...EXCEPT, I don't find there's anything particularly superior over conventional designs concerning those claims - Theoretically. But, Practically - that may be another matter. For example, it's true that conventional box designs (with conventional drivers) are going to sound perfectly fine AS LONG AS THEY'RE SET UP IN A PROPERLY SIZED, PROPERLY PROPORTIONED ROOM! But, this is not everybody's circumstance, certainly. Well, maybe some people did not think the original problem through and overbought the speakers that would integrate into their room. But, then again maybe the room in their home is a horribly funky shape, or too small, or whatever and they're just stuck with it. But, that's a case in which it's very likely to hear a comparatively clear improvement with dispersion restricted speakers. But, what I'm saying is, that makes their advantage primarily a practical one not, in truth, a theoretical one, as I think some would believe. Your stage does collapse as you move off axis, but the quality of the stage depth, width, height and placement, I don't believe, can be said to be any worse or better at the LP than the properly implemented conventional approach. It's how problematic the room is that should be the determining factor. No reason that restricted dispersion speakers cannot be used equally well in ideal rooms, either, but I think their real advantage over conventional designs is their use in truly "problem" rooms.
Apart from that, it may just be a matter of room treatments, if needed.
But, generally, bass problems have different causes and solutions than reverb and echo. In part that may have more to do with the fact that, to our ears, sound becomes basically more directional as frequency rises. When you start getting up into the midrange you're getting into the area of noticeably increased dispersion. Dispersion is usually greatest with Omni-directional types (some Walsh, Atmosphere...). Next, in order of decreasing dispersion, would likely come the dipoles. Then may come standard, box monopoles that use conventional cone or dome drivers. If their crossovers are up to par, they usually have rather wide dispersion in the room, those with narrow front baffles may be thought of as having the widest among them. Those monopoles that use non-standard drivers (like ribbon tweeters or midranges, for example) may have noticeably less wide dispersion than with conventional drivers, though. Last, I suppose, would be the speakers that have been specially engineered by the maker to be narrow dispersion speakers, or may have a specially designed apparatus attached to the baffle that is meant to accomplished this task. That would be speakers like those from Emerald Physics, Wavetouch, VMPS or any other design that uses an array of horns or waveguides, etc for that purpose.
Lots of manufacturers will give you the spiel about how restricting the width of the dispersion in the room will greatly reduce the effect of interactions. IME, a well designed conventional monopole can have (in a good system) a "true, 3D, walk-thru soundstage" as you may have read of before. The restricted dispersion designs can have just as great a soundstage at the LP, it's just that if you move much off axis, or stand up and walk around, the stage collapses.
Otherwise, what is said about the advantages of restricted dispersion designs I believe is pretty much true...EXCEPT, I don't find there's anything particularly superior over conventional designs concerning those claims - Theoretically. But, Practically - that may be another matter. For example, it's true that conventional box designs (with conventional drivers) are going to sound perfectly fine AS LONG AS THEY'RE SET UP IN A PROPERLY SIZED, PROPERLY PROPORTIONED ROOM! But, this is not everybody's circumstance, certainly. Well, maybe some people did not think the original problem through and overbought the speakers that would integrate into their room. But, then again maybe the room in their home is a horribly funky shape, or too small, or whatever and they're just stuck with it. But, that's a case in which it's very likely to hear a comparatively clear improvement with dispersion restricted speakers. But, what I'm saying is, that makes their advantage primarily a practical one not, in truth, a theoretical one, as I think some would believe. Your stage does collapse as you move off axis, but the quality of the stage depth, width, height and placement, I don't believe, can be said to be any worse or better at the LP than the properly implemented conventional approach. It's how problematic the room is that should be the determining factor. No reason that restricted dispersion speakers cannot be used equally well in ideal rooms, either, but I think their real advantage over conventional designs is their use in truly "problem" rooms.
Apart from that, it may just be a matter of room treatments, if needed.