To Tab or Not to Tab......
I think the major difference is the thickness of the material, paper or card.
Paper models usually have tabs whereas Card models don't.
Tabs are great for easy building (for kids), rapid building or prototyping, in my paper designs I Always use alternating tabs to allow me to align parts better, because the thickness is less, the step problem isn't that much of a problem really. In my prototyping white card models tabs are used and glued to the outside to make a cleaner mold.
I also design paper models without tabs, they do look alot better, but you need to take more care when building them if they contain alot of curves, get it slightly out of line and you mess the model up completely, which is heartbreaking if your close to finishing. Paper tends to warp more than card when alot of glue is applied.
You can cut the tabs off if you don't want them, alot of people do that.