Whilst in general, vertical radiators won’t provide as high a heat output as horizontal radiators, everything is relative with regards to whether or not they give out enough heat.
Use a BTU Calculator to work out if your preferred vertical radiator design provides an adequate level of heat to warm your chosen space to a comfortable temperature.
It might prove the case that a vertical radiator is actually a much better option regardless of the lower overall heat output it delivers, depending on the layout and size of the room it will populate.