Theoretically there shouldn't be that much difference. Putting 2kW of electricity into ny heater should produce (almost) 2kW of heat. The 'almost' there is because of losses powering the fan in a fan heater or heating the metal (rather than the air around the heater) using other types of heater.
However (other than when I was in a hall of residence at college) I've never lived anywhere with central heating and nearly always had to rely upon portable electric heaters. I've found that, while they're best for getting an initial 'boost' of heat, fan heaters cost more to run than other types of electric heating. (They're also noisy and tend not to last very long either). Although they cost more in the first instance, I'd now only use oil-filled radiators (unless I had a lot of money and could afford the outlay for an 'oil-free' radiator, which get really good reviews).
However I assume that youre planning on using your heater in a bedroom which will also serve as a study, playroom or similar. If you're only going to sleep there you shouldn't need any heating at all. A nice warm duvet is far cheaper! (I've only got a single oil-filled radiator, in my living room, to provide all the heating in my house. I turned it on, for the first time since April, earlier today and I'm feeling really cozy now!).