The two kits are supposed to be of the same boat but you cannot compare them: the Dumas Akula is a pool toy, made out of plastic, and whose dimensions/appearance are really vague, it is a dynamic diver and you only need a 3 or 4 channel radio to control it.
On the other hand the Engel Akula is a very accurate representation of the russain boat, made out of fiberglass, with scribe lines, retractable bow planes, periscopes, piston ballast system, etc.... This boat can be made to be extremely nice.
The choice mostly depend on how much experience you have and how accurate you want your model to be: the Dumas is a pool toy but pretty easy to put in the water and you can probably play with it in a few weeks. The Engel is a lot more complex and will require a lot more time to complete, as well as skills. If you are a beginner with no experience the Dumas would be better, however if you feel like you can learn new things easily and are not afraid to ask for help when in tight spots, the Engel is for you.
There are 10 kind of people, those who undertand binary and those who don't !