To answer two questions,
A, Ecoburn insets, They are a radiating stove only, so the front lump of metal sticking into the room gets hot and thus radiates heat into the room, thats it.
A convector inset does that AND convects air drawn into the bottom of the stove from the room via an air gap between the firebox and the outer case around the other three sides and back into the room above the door thus using all four sides of the stove to create heat coming out into the room. Upside of a radiating inset is a slightly wider firebox so can take slightly bigger logs. Output figures are fairly accurate.
As such if the stove is wanted to wack out lots of heat, perhaps in a large room then a convector would be better at doing this. However if its more for effect or in a smaller room then there should not be an issue. They do burn well and can be installed without a flue liner but I would strongly advise installing a liner to make the stove as efficient as possible. Make sure that you infill loose insulation material around the stove and lower part of the liner to make sure that no heat is lost up the chimney from the stove body. ( tip it in from the top of the chimney after lining) Given that happens all should be well providing the stove is correctly sized to the room.
B, The Esse Insets, Esse were the first company to develop the inset stove ( so they say !!) to replace the old Parkray fires. The 301 and 350 are convector insets so all 4 sides used to produce heat, they produce so much heat if driven hard on solid fuel that extra precautions are advised re extra expansion joints in a hearth and possibly the back plate. The heat output ratings are I feel a bit conservative.
I act for both Arada ( Ecoburn) and Esse, its always the lady that chooses what she wants, I would sell twice the number of Ecoburns as I do Esse's and dont have problems with either but I am carefull to ensure that when installing the Ecoburn we line and infill with insulation.
If you are intending to line the Ecoburn install you need a connector from Arada as the outlet on the back of the stove is letter box shaped.
Hope that helps and puts your mind at rest, fuel it with DRY logs, nothing over about 16% MC and the dryer the better and it should work fine.
A