It depends on your definition of neutral. “Neutral bass” in a home HiFi system, movie theater, outdoor rock concert, music studio, or in a recording booth will all sound quite different. Add to that, the shape of your own ears emphasize and de-emphasize bass, mids, and highs differently from literally everyone else on the planet, some people have VERY unique ears.
The Sennheiser HD 25 is a pro headphone made for use in recording booths, DJ’s performing live, and it even has a history as sound blocking headphones used by passengers in airplanes. The midbass is moderately elevated if you look at a graph, but most people find it a pleasant and not aggressive headphone, and not loose or boomy (though it’s not the sharpest headphone either). You may find that it clamps firmly on your head: this helps with the sound isolation and to prevent the headphone from slipping around while you’re walking (or performing), but it might be too tight to comfortably wear for 5 hours straight for some people. It’s also extremely tough, durable, and easy to repair. It’s a popular, well-loved headphone, historically one of Sennheiser’s most popular.
I personally am surprised how much I like the very serious looking Sennheiser HD 280 Pro, that is fairly “natural” sounding and easy to drive with my iPad’s built in headphone jack, but that is a full-sized headphone that has its pads resting around your ears rather than pressing down on them (which is why I prefer full-size, over ear headphones).
The DT1350 is more for mainstream consumers than working pros, with fancy looking metal parts, and a more “musical” tuning than “reference/analytical.” A bit more bass than the HD 25, as
@plakat mentioned, but it’s of a nice quality and not heavy-handed. As was mentioned before, the sensitivity rating is much more useful for determining if a headphone doesn’t need a powerful amp and if a smartphone dongle will be enough; a little bit of impedance can actually be a good thing, and help lower distortion in some kinds of amplifiers/amps.
When an audio enthusiast says a headphone has extended bass or reaching low, that doesn’t mean it has extra bass emphasis. A headphone without bass extension actually has the bass get “quieter than neutral” as you play lower and lower frequency notes, some you can’t even hear the lowest notes because they’ve been rolled off and are too quiet.
A lot of people focus too much on bass reproduction. They often think that the way bass is presented: louder, more detailed, a sharper and harder attack at the beginning of a note, shorter decay, etc are the main hallmarks of whether a headphone or speaker is good or not, usually because cheap headphones (like “free” or cheap earbuds) can’t produce extended bass and using any EQ to raise the higher frequency mid-bass causes a lot of distortion and loose boomy sound with a lot of resonance. While it’s true that having Goldilocks bass that is not too hot and not too cold is a good thing, and entry level Hi-Fi headphones and up (mid-fi and summit-fi) are usually much better at reaching low bass notes without distortion problems, it’s also very important to consider the midrange. Mid frequencies are where you hear all vocals, and most instruments, so this is a critical range to get right in order for the music to sound “natural” and realistic. Bass and Treble are like the “special effects” that add excitement to music, but mids are where the music is.