I owned a JVM410, 205, 215c, have played the 50w Badlander several times, and just purchased a Badlander 25. Both have awesome tone and flexibility. I don't get the criticism of the JVM, and comments that the Badlander is "better" just don't make any sense beyond someone's personal preference. They are apples and oranges in terms of sound. When it comes to metal, the JVM has incredible tone in orange and red modes. You can do anything with a JVM and it will sound amazing. Channel 1 is often overlooked though it sounds spectacular. One of the things that turns people off about the JVM is the digital reverb. I don't think it's particularly great, and think that when people judge the tone with the reverb on, it kind of skews their opinion. I use a Strymon Blue Sky reverb and it sounds way better and more natural than the JVM reverb. Then you always hear from the Marshall vintage guys, plexi purists, etc. who rag on the JVM and say it doesn't sound anything like an 80s JCM800 or 60's plexi, blah, blah. It most definitely has that tone because the circuits are built into the JVM, and you can certainly get the vibe of their older amps. Where the differences really are is mainly in the JVM's unique midrange and overall tighter structure. You can do a whole lot with them, and there's a couple of features that they offer, for example, channel 1 green mode excludes the channel volume. The EQs can also be rolled up to 10 like any other Marshall and get some great sounds. Even though the JVM has little buttons and things, I've found them to be quite reliable.
The Badlander is not really a 2 channel amp in the conventional sense because it mirrors one channel. However, it's quite versatile in that it offers 3 modes per channel. When the 2010 Rectifier Reborn came out, I thought the changes they made were superb. When the Badlander came out, I was scratching my head a little, but still impressed with the sound. In my opinion, all Mesa Boogie amps have great clean tones. The Badlander also has a beautiful clean channel. However, there is a sort of modern element that I find hard to articulate. The gain channels are incredible, and definitely reminiscent of the Dual Rectifier. One of the best things about the Badlander is how easy the EQ is to use relative to other Mesa Boogie amps. It does sound tight and less low end than the Dual Rectifier but I don't think it's missing any low end. It's like the most dominant lows are combed back. It has very good definition at high gain. It also lets you get really great lead tones in crunch and high gain modes.
The Badlander is versatile but does have it's limitations. In my opinion, the Rectifier Roadster is the best Rectifier Mesa ever made. I do miss that amp a lot, and am uncertain if the Badlander can become my new favorite rectifier. Nevertheless, I'm really liking the way it sounds and itching to put my Badlander 25 through some loud testing. You can't go wrong either way. The JVM can do both vintage and modern tones but not really so with the Badlander. The Badlander has the Mesa Boogie Rectifier thing going on which is quite unique, but the JVM is also quite unique. As I always say, if you want a rectifier sound, get a rectifier. If you want a Marshall sound then get a Marshall. If I can offer any advice one way or the other, I'd say get the one that's the best deal because amp prices are through the roof!