Well I guess they are all tough to clean when very dirty, but for me, I find the Smeg oven a challenge, closely followed by Flavel. There is something about the enamel on a Smeg that just makes it very hard work to get clean. The carbon really sticks to it like glue. There are also a lot of ridges around the bottom sides of the oven and behind the back plate, as well as above the grill element, which only makes it harder to clean.
These ovens have very fiddly little bulb covers too, located right in the top corners which makes it very difficult to get them out if you need any sort of leverage to turn them if they are stiff.
The doors as mentioned earlier in this blog cannot always be cleaned completely due to a design fault, but even the ones that can be cleaned can still be tough to clean as the dirt does not come straight off the glass as easy as on other makes. A lot of the doors are glued into a recess which means you cannot clean around the edges of the glass and always end up with a small amount of water between the glass and the door.
As most Smegs are made with shiny stainless steel that has a lacquer on it, this can over time also start to peel, so you have to be very careful when cleaning not to make it any worse.
The storage drawer below the oven often collects all the drips and food debris inside it. The drawer is painted so again when cleaning this it is a fine line between cleaning it and having some of the paint wear away.
The control panel and buttons often have transfers which over time have been worn away or will wear away easily if you use anything abrasive to clean so it is often a case of painstakingly trying to clean around all the numbers.
Smeg ovens are definitely one of the hardest to clean in my opinion and it is always a time consuming job, especially when cleaning the ranges.