Kit Manufacturer Quality

IMHO from the kits that I've actually built,  & recent kits only:

Aircrafts:

1.  Hasegawa

2. Tamiya

3.  Hobbyboss

4. Trumpeter

5. Revell Germany

6.  Revell America

WWII Armor:

1. Dragon

2.  AFV Club

Modern Armor:

1.  Tamiya

2.  AFV Club

3.  Hobbyboss (not built, but in stash)

4.  Trumpeter (not built, but in stash)

Ships:

1.  Tamiya

2. Trumpeter (not build, but in stash)

3. Dragon

It's a question of money. There are good cheap kits and lousy expensive kits, but IMO most good kits are expensive.

If your primary concern is fit and overall engineering quality, it's hard to go wrong with Tamiya.

Their armor kits are almost universally recommended as the best way to get into tanks and such.

Their aircraft can vary - and they do have a few dogs - but their 1/48 single-engine props generally exhibit excellent fit. And in those you have a few that are somewhat dated (Fw 190) and a few that are among some of the best kits ever put into a box (P-47). But they all fit pretty well, and most of them can be picked up for around $20-$25. The P-47 will be closer to $30.

In 1/32, Tamiya's new Spit and Mustang are amazing, but I would't recommend them until you've got some kits under you. The fit is spectacular, BUT they are very involved kits, and even with everything snicking together you have to pay a lot of attention to what you're doing.

If I had to recommend one, it'd be Tamiya's 1/48 P-51B (or Mustang Mk.III if you want the RAF version). A gorgeous kit on just two sprues. Fit is impeccable. And you can find it for $20 online.

Now getting out of here before the Monogram Mafia sniffs this thread out!

Another nod to 'google reviews of the specific kits you're interested in' angle.  If you want to build aircraft, espcially in 1/32 scale, then any newer Tamiya kit is going to be close to perfect.  Their mold quality is so high that putting together a Tamiya spit, mustang, or zero is considered by some to not even be 'modeling', but simple construction.  The price of their kits generally reflect the quality, however, so you're directly trading fitting time for money.

Trumpeter and Hasegawa... you need to google the kit.  Here, LSP, Hyperscale, etc. between them have reviewed pretty much every kit in existence, and you'll immediately see the good ones from the problem children.  My first kit back was the Hasegawa 190 D-9 in 1/32, and I researched it extensively.  It almost fell together, with only a few seams to challenge my nascent skills.  I didn't research the next kit up, the Hasegawa 109 K-4, nearly as well, and it was a nightmare.  The next two were Trumpeter, the Me 262 A-1 and Mig 3, and they both got good reviews and indeed went together well especially in the large, important parts.  

Decide what you want to build and in what scale, and then google reviews on it.  

I take it that you want a kit that you can build easily, rather than beat into submission?

All of the kit makers are going to have well-engineered kits that fit together like they're supposed to, and they're also going to have their share of problematic kits that will fight you all the way to the finish line.

Tamiya is likely going to be the most recommended manufacturer for your needs, as they have an excellent reputation for well-engineered, high-quality kits in all areas of interest.

What are you looking to build?  Cars, aircraft, armor, ships...?   What one company does well in one field they might not do so well in another... Dragon does excellent, if not fiddly, armor but their aircraft can be real PITA's that require a lot of work to make fit right.  Not to mention their instruction sheets can make a stone statue cry in frustration.

Best thing I can recommend is that you inquire about specific kits of a given subject- that way you'll get the most useful feedback.

In my humble opinion that is indeed a very subjective question.  Certainly there are manufacturers that do a better job than some others, but many of the worst in this category also are the ones that offer the most interesting kits. 

From personal experience I can say that I have always had good luck with the fit of Tamiya, Trumpeter, Italari, and Hasagawa kits.  Typically for most LHS purchases, the more the kit costs the more detail went into it's production and the better the quality (don't depend on that though!).   

My real recommendation is to Google kit reviews of any kit you are interested in before you buy it to see what others have said on it's fit and finish.  Also in the in-progress builds on this site, you will start to see certain manufacturers mentioned over and over as quality producers.  I try to always do this and it has saved me from a few kits that after reading the reviews and in-progress builds were well beyond my skill level.  It also helps so that I can make sure that what I am getting isn’t going to be the one model from that manufacturer that isn’t worth spit.