The P5 and ES10 are better as far as portability is concerned. The SRH840 is massively more massive IMHO, and their cable is problematic.
I've tried the P5. I do think it probably is one of the most brilliant piece of design I've ever come across in audio in terms of usability : it isolates very well, and is full of actually useful gimmicks like magnet pads or detachable cable running from one side only (good if you're tired of entangling cables in your vest zipper). Build quality is off the chart in its price range (much better than the Audio Technica ESW10 and ES10 for instance). However, audio-wise it feels a bit overpriced : it is technically in the SRH840 / HD25 / etc. camp, not the ES10 one. It also has a very smooth, soft and slow sound signature, which works quite well with acoustic / classical / jazz, but badly with rock / metal / fast paced music, though it might vary depending on your source.
I've never tried the ES10, but I currently own the ESW10 which are very likely to be in the same SQ bracket. It therefore should be a nice upgrade in comparison with the SRH840 and P5. However do note that it won't be earth shattering in terms of difference, especially if your source isn't up to the task and your files badly encoded. Also, it is likely not to isolate as well as the P5. Sound-wise it should be much more appropriate for rock / metal / fast paced music than the P5, and probably better overall for most genres actually. Their sound signature is different though.
You should give a look at the T50p. They're gathering mixed reviews, some say they're SQ wise in te HD-25 camp, or lower, others put them up against the ES10 / ESW10. Some even said they're more detailed than the ES10. Very controversial, and therefore worth a try
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