I'm currently on my third Trumpeter kit, and have no serious complaints about any of them. The fits of the parts is generally excellent and their attention to detail is excellent. Even wing to fuselage fit seldom causes a problem. My only complaint is that they tend to put ejector pin marks in some of the hardest places to get rid of, but that's a problem with every manufacturer.
They do tend to have a lot of detail in areas that get covered up so you have to watch out for that. The engine of the F-105 is very highly detailed but once in the fuselage you can't see very much of it. Same for the P-40. I spent a lot of time adding ignition wires only to find out that once the engine is installed there is no way for them to be seen.
They usually have numerous options for assembly as well. Radar installations, refueling probes, speed brakes, etc. can be installed open or closed. Ailerons, flaps, spoilers, elevators, and rudder are normally hinged and can be set in any position.
As to decals, I didn't use the box decals for my P-40 and haven't put them on my F4U-1D or F-105G yet. The decals for the F105 were done by TwoBobs but I did see a post in the decaling forum that the yellow bands for the ordnance don't fit properly.
I've never built a Hasegawa kit so I can't compare Trumpeter to them, but I would never be reluctant to buy another Trumpeter kit based on my past experience with them.