I'm writing this to clear up some of the confusion I see on the subject of how various Battletech paint jobs look. Most of us including myself don't have much of an art theory background, so we just gravitate to particular styles without really thinking about it. This has some consequences, especially if you don't think much about exactly why a specific painting style is so appealing to you. I chose to break this down into two broad categories because it seems like the appropriate dividing line for what I'm talking about. Obviously to some extent you can use specific techniques to achieve either style and miniature painters often deploy all of them to varying degrees. (Cockpits are frequently done with some form of stylistic approach while bases are almost always dry-brushed)
Naturalistic This is a gritty, subdued, "earthy" style that often features a lot of textures and muted colors. It's the classic "scale modeling style", or the "Forgeworld" style. It's a very old way to paint everything from railroad scenery to military models and you'll see a lot of it in the classic Battletech books or with painters that have been working in the hobby for a long time. It's experienced a bit of a resurgence with the aforementioned Forgeworld models and Horus Heresy universe in Warhammer. Dry-brushing, washes and weathering are frequently employed, while edge-highlighting is kept minimal or even omitted entirely. The idea is to try and represent how a model would look in real life if one were to paint it much like a real life object.
B1BFlyer, Camo Specs On the plus side, it is indeed more "realistic". It's also how nearly everyone paints their background terrain, so 'mechs painted in this style tend to visually gel with their bases and backdrops. (Whether that's ideal or not is another question) It's an often gritty, dirty style that looks how you'd imagine a warmachine in the 31st century to actually appear in real life. It uses techniques that are frequently faster and require less brush control than other styles, although I want to make it very clear that even dry-brushing can be taken to an elite level. In other words, the entry level skill threshold might be lower, making it attractive for new painters.
On the negative side, 'mechs painted this way can often appear a little too messy and indistinct for some tastes. It's not usually as "readable" as the other major style, which is why Games Workshop doesn't use it for showcasing their own models. Color depth can be a problem, with miniatures looking "flat" or "boring".
Stylistic This is how I paint, it's well known as the "Eavy Metal Style" and it's likely the most popular art direction in miniature painting as a whole. The goal is not necessarily to capture how something would probably look under normal lighting conditions, but to accentuate and exaggerate the shapes, lines and details of the model so that it "pops". Stylism is all about grabbing your attention first, and looking strictly realistic takes a backseat. Edge-highlighting and blending are the dominant techniques.
Arclight, Camo Specs The advantage to this style is that makes the miniature very "readable" or legible even in imperfect lighting or from a distance. The lines do indeed pop out and allow the viewer to instantly pick out the major features of what they're looking at, which is very important when you're working at such a small scale. Color depth is usually rich and phenomenal, particularly if you're following the 'Eavy Metal tactic of highlighting all the way up to pure white. Even with no washes at all miniatures painted this way tend to never look "flat". It's visually a very arresting, clean, and eye-catching style.
The downside is you are throwing some degree of naturalism out the window. Every edge of every single panel of armor technically should not have a fine edge highlight. To some tastes, this style looks cartoony, over-worked, and "toyetic".
It can also be extremely time-consuming and requires insane levels of brush control. You're gonna be blocking in the base color of every panel then carefully lining it with progressive highlights, which takes forever. Finally, it does contrast against the bases and backdrops most people use. Whether this is good or bad depends on your perspective.
Other considerationsBattletech is 6MM scale. While the size of the miniature might be comparable to something from Warhammer 40K, it's meant to represent something much, much larger. This can be somewhat difficult to convey. I think the more you can add tiny details like caution stripes, unit numerals, decals, and insignias the easier it is to get this across. 6mm scale terrain and vehicles to give the viewer a visual reference point also really helps, as does photographing from low angles. (Be careful not to just reflexively photograph miniatures as you would a collection of small tea cups)