From a purely technical standpoint;
Ares did not make sense. Maybe in its original form, it made some sense, but even then, there are many criticisms about the Exploration Systems Architecture Study.
But it soon deviated and evolved out of control. Ares I changed to the 5 segment SRB, and from a (dubiously possible) airstart SSME to the lower performance J-2X. It encountered issues relating to abort scenarios and vibrations and lift capability.
Ares V changed from SSMEs to RS-68 engines. Then its core was widened to ten meters. Then stretched, along with the SRBs, necessitating a '5.5 segment' SRB. Then it was discovered that the ablative nozzle of the RS-68 would not withstand the thermal environment between the SRBs...
All the while, everything kept along on the same course and did not deviate. Presumably the people involved were too proud of their idea to chuck it in the bin... or there were other political forces that made even a technically similar solution unpopular.
Eventually Constellation was cancelled, I believe as recommended by the Augustine commission, but not due to technical issues- rather due to unrealistic cost expectations.
Technically, SLS is more similar to the DIRECT concept proposed as an alternative to Ares, but is really just 'Ares V classic'. It does not do the same thing as the Ares rockets; it has lower payload-to-LEO capacity than Ares V, and higher payload-to-LEO capacity than Ares I (which did exactly the same job as existing vehicles and was sold only on dubious safety assertions).
So in a comparison to Ares as it ended up, SLS is better. But as a whole, its technical merit is debatable. Since it will have a low flight-rate, it will be at an economic disadvantage to smaller vehicles.
There are also alternatives that could provide heavier lift capability... such as ULA's "Atlas Phase II" and as a more remote possibility, SpaceX's "BFR" Falcon.
But politically, SLS is a complete and utter travesty. Instead of asking NASA to formulate mission plans and financial and chronological requirements, the Senate/Congress has mandated to build a vehicle with a 70-130 ton payload capability (which is just there because it implies SDLV), without any clear payload for it.
And on top of that they have demanded it be "Shuttle and Constellation derived", regardless of whether this would actually be helpful in a legitimate sense.
It does not help SLS's legitimacy that the politicians who have "fought" for it are senators of states that would be benefitted by such a program.
There is no study, there is no suggestion, and even if there was (somewhere), it is just a big mystery and we're not able to get our hands on it, pick through it, and scrutinize it. It is all just "studied" by the congressional rocket scientists...
SLS is sucking up billions of dollars in the next few years, and the only concrete mission is a meaningless Apollo 8 recreation. Without money for actual space exploration technologies, there will be no space exploration at all and a large launch vehicle will never grant it.
It is just so wrong, it is horrible.
