Basically same thing? Maybe you mean monolight? I like them all but speedlights are convenient, mobile and battery powered. Also they are relatively cheap.
For portraits, I think there best lights are AC-powered studio flash units, with fairly powerful built-in modeling lights; something like 150 Watt-second monolights, three, or four, or five of those make up the old-school, standard "professional lighting kit", where there is a main light, a fill light, a hair light, and one, or two background lights.\
Studio flash units are 1)monolight type (Alien Bee 400, for example) or 2) pack and head systems (Speedotron Black Line power pack and individual light heads, like fan-cooled 102 units. The biggest advantage is 1)modeling lights in the flash units, so you an literally SEE what the flash will do, and also, you have LIGHT (from the modeling lights) to focus with in an indoor environment. But there are other advantages too: ease of modifier attachment via speed rings and umbrella shafts, high power output, designed for longer sessions without overheating, and a wide range of light-shaping tools designed specifically for each system (grids, barn doors, shoots, diffusers,beauty dishes)--and those light modifiers attach securely.
Speedlights: harder to learn on, fewer light shaping tools,but small, light in weight, easy to pack, battery-powered, some systems have some NEAT light shapers made for them as well as some higher-powered units at high prices. (Godox, Canon 600 radio series)
Total price of systems is higher for most studio flash units, but then also more powerful, and can do more things, more easily, with less "rigging: than with speedlights. Look at Profoto's immense lineup of light shaping tools, or look at those from Paul C. Buff or Speedotron.