First and foremost, I buy for quality - but I try to get the best price I can find.
Most of the time that comes with a name brand and line but not always. Bachmann Spectrum generally makes very nice steam locomotives. But their diesels in the same line, for some reason, are NOT of the same quality. And sometimes that can even be said of like locomotives of the same brand and line.
Generally speaking, the following brands and lines are categorized from fair to excellent quality:
Fair:
Bachmann “Standard” (Best to avoid)
Model Power
Good:
Athearn “Blue Box” (Good runners - good detailing - slightly noisy)
MDC (Nice but older technology)
Rivarossi (Nice looking but hit and miss with operations)
Better:
Proto 1000 (Same motor but not as good detailing as Proto 2000)
Best:
Atlas: Gold line (Very nice detailing and smooth runners)
Athearn “Genesis” series (Very nice detailing)
Bachmann “Spectrum” series (Steam better than diesel)
Broadway Limited (BLI) (Very nice detailing - generally very good runners)
Kato (Smooth runners - modern diesel - no steam)
Precision Craft Models (An outcropping of BLI - fairly new but supposedly good)
Proto 2000 (VERY nice detailing than Proto 1000)
Stewart (VERY smooth runners - good but not great detailing)
Trix (Exquisite detailing, VERY smooth runners and nice detailing)
Always check around for pricing. You can generally find some pretty amazing deals online if you dig around, are patient and willing to wait for the price to drop. I would also encourage you to find a good LHS and support them as much as you can.
It really depends what you want to model, steam or diesel. different manufacturers make different things. I’m only going to talk about modern diesel engines because that is what I model and what I know. Somebody else will have to fill in for steam.[:)]
If you are looking for modern diesels, the BEST are Katos. The run smoother and quieter than anything and the detailing is top notch. But you pay for it, I buy most locos discounted and usually pay about $80 for a Kato.
The best VALUE in my opinion for diesels are the NEW spectrums. The old ones arent great, but Bachmann started over with the new engines and they are great. Not quite as good as Kato, but due to bad reputation you can pick one up for $30. What a deal!
P2K (proto 2000) are also very good. Again not as good as Kato, Id say on par with the spectrums. I only buy the older P2Ks because the new ones are way overpriced IMO. You can tell the old ones by thier large, light blue box, the new ones come in silver boxes.
Athearns, both RTR and blue box are pretty nice engines. The RTR are the better of the two. I dont buy many athearns because I like to run sound and they are just too noisy.
Athearn Genesis are probably the best detailed engines around. I owned 3 of the SD70MACs and had to do lots of major surgery on them just to make them stay on the rails. And again they are noisy. I dont buy Genesis because there are just too many problems with them. If you do buy a Genesis loco DO NOT get one with factory installed sound. They use MRC decoders which are about the most worthless things you can imagine.
Broadway Limited makes engines with factory installed sound. They have good detail, run well and the sound is pretty good. But they will cost you. If you want a diesel right when it is released you can find it for about $200. Wait a year and its $175. But they are a quick way to get sound if you dont have the skill/desire to install it yourself.
There are many different types and kinds of manufacturers. Also consider what your budget is and if you want to stay strictly to American models vs European models.
My American pic’s are Bachmann, Proto 2000, Lifelike, Atlas and Athearn (formerly MDC) and some Model Power (formerly Mantua).
In the European market my favorites are Roco, Marklin, Fleischmann & Micro-Metakit (Super expensive). Overall, I think the european makers put more detail and craftsmanship than their American counterparts. The more expensive models consist of metal components such as brass and pewter - but then again you can pick up a beautiful plastic model with almost as much detail as the high end brass models with today’s technology. Whatever you decide - have fun and there are plenty of members in the forums to help you out with any questions or concerns.
Like anything, you get what you pay for… That being said, there are some good deals out there. As for Steam, well I like Rivarossi and Bachmann Spectrum; as for diesel, I am far from an expert, but Kato (my favorite!), P2K and Stewart (very nice!) are all great. There are some odd others (e.g. Lionel, yes they make HO) that make great products (that sometimes take a bit of “tweaking”), depending on the model. The guys here are great assets when asking about certian models.