The Tu-204 is somewhere between the Il-38 and Tu-142, while the Il-114 sits between the Be-12 and the Il-38. Il-114 would be good for the Baltics, even the Black Sea. Tu-204 for "open ocean" missions.
Another factor is speed, the Tu-204 is faster so it can get to places further away faster, but the Il-114 can operate at lower speeds which should make chasing down enemy subs easier and more efficient.
It should also be rather cheaper to buy and to operate.
The question is whether having 2 different platforms (and soon UAV one) makes economical sense?
There is a wide variety of requirements... some of which are contradictary... remember the Russian Navy used three MPAs... Be-12, Il-38 and Tu-142, as well as Il-20 and Il-22s for some roles too, so using a few new ones wont make it more complex and problematic.
I still would like to understand if there will be also a niche for a modernised A-40/ Be-42.
The fact that they are extending the operational lives of the Be-12s seems to suggest they have value and need replacing... certainly even just for fire fighting and operations at sea an amphibious aircraft has value.
It also has certain costs so the solution would be the combination of likely uses with the likely probability of its use factored in vs known costs to buy vs potential costs of needing it but not having it... complex but not impossible.
I think this project is over
They do have the Be-200 and the introduction of families of a range of engine powers and types means a potential heavy replacement is possible... but not certain.
The Il-114 will be produced in civilian versions. There is an Il-114 flying around for Radar-MMS fitted with tech for ASW. Shouldn´t be that complicated or expensive to produce 20 - 30 for the Navy.
I find it more expensive to use a "big" plane like the Tu-204 for short-range ASW.
I suspect the Tu will replace the Tu and the May and perhaps a stretched Il-114 might perform short range MPA/SAR replacing the Mail.
The question being will they want long range (A-40) or medium range (Be-200) amphibious aircraft for SAR... an amphibious aircraft would be an ideal way to launch and retrieve unmanned under water vehicles... it could also be fitted with a dipping sonar too.
That's not the same role then. And coast guard could be interested by a SAR aircraft.
There is enough variety in roles and location to operate more than just one type together with UAVs and UUVs etc etc.