What kind of portable electric heater should I use in my kitchen?
The most important issue in a portable heater, even before the issue of heating is safety. Dangers involve tipping, brushing a hot surface, things falling into, in or on it.

This risk is even more pronounced in a kitchen which is a busy place (unlike a quite reading room). People move about, often quickly and carry (and drop) things.

While your particular room setup may allow any of the above types to work, I might be inclined to get an oil filled because they have little risk of things being harmed by brief contact, and seem fairly safe if tipped (although I think, in the US, all modern types require auto cutoffs if tipped).