I've owned both and ultimately ended up giving my x3 away to my brother. Here is my take:
-The x3 is warmer, no matter what FW you use for the x5. For a while, the x5 in comparison was colder and lacked some bottom end which may have contributed to it feeling colder. However, with the new beta firmware 2.02 (for the x5) the x5 is warm enough for me to like.
-The x5 is superior in detail, clarity, and brightness. No matter what FW I upgraded the x5 with, those characteristics stayed the same. The x3 simply cannot compare in this department. However, the x3 got 1 step closer with the last firmware I upgraded it with (2.14b) before giving it away. That last firmware made me think long and hard about giving away the x3, but I did so anyway because although 2.14b was good, it was still buggy and freezes up alot. 2.14b really improved the value of the x3 sq-wise.
-Bass-wise, the x3 is naturally the winner in terms of impact and depth. I say naturally however because the bass is consistently good during each FW. So depending on what FW you upgrade the x5 with, the x5 can easily match the same bass impact and depth, but with added detail. Some people liked it when certain FW upgrades got rid of the sub-bass(or mid-bass? Maybe I'm actually a mid-bass head?...lol) on the x5, so it can be a pro or con depending on what side you are on. The flexibility of the x5 to get rid of bass/regain bass by simply upgrading FW adds alot of unintended value to the x5 hilariously enough. This means it can cater to the pro bass/bass hater crowds...bugs are a different story.
-The sound stage on the x5 is a bit larger than the x3, and sometimes make my jh16's sound airy which I didn't think could happen. Also the 3d presentation is better on the x5, you can actually tell that some instruments are behind others, instead of just being blended in.
-The UI on the x3 although is workable, is clunky, slow, and a pain in the butt to get around. The x5 UI is alot faster and more responsive, and that wheel makes things so much easier. Also, on the x5 you can easily switch back and fourth between the main menu, sub menu, and current track without loosing track of what folder you are currently playing from. It was annoying as hell trying to switch to a different track on the same folder on the x3. You had to manually go back and navigate from the 'folders' menu whenever you wanted to switch to specific tracks from the same folder because the x3 forgets what folder its playing from.
So now I'm tapping my toes to the visceral bass of the x5, while at the same time banging my head to the high-hats on the other end of the spectrum. I've never done that before with my previous ipods, zunes, sansa clip, nor x3 (not until 2.14b anyway). I stuck with fw 1.21 on my x5 for the bass, sometimes yearning still for the bass rumble that I could feel in my chest that was found only in the x3. But not anymore, the latest fw 2.02b brought back the same awesome bass that i oh-so-missed, but with much better presentation. It was such a surprise and joy to be listening to it all day at work. I knew then that I will not be looking back at the x3 anymore, as long as I don't upgrade to the next FW anyway haha. The difference in bass between FW upgrades is no joke, and can be easily more noticeable with an external amp w/bass boost.
Overall, the x5 seems to be more dynamic, clear and detailed and easier/friendlier to use. The X5 doesn't fall behind in any area sq-wise in comparison to the x3, and actually excels in alot of areas. Enough so that you could be justified in paying that extra $150 to go straight for the x5 instead of x3. Its a straight up steal. HOWEVER, it depends on what ear toys you will be using it with. If you have a low to mid end headphones, the x3 should do just fine. If you have a high end headphone, you could get either x3 or x5 and be fine, but you will not be getting the most out of your expensive head phones/buds/iems. I ultimately gave away the x3. Because although both are fun-- detail and clarity(and ui) wins in the end. If you really cannot afford the x5, then by all means get the x3. Not that the x3 is a bad choice by any means, I loved it when I had it.
Also, get an external amp if you can. The internal amp on the x3 and x5 although are good, just aren't as good as the high end amps. I use the jds c5 amp because on top of being more dynamic, it has that awesome bass boost function. I know I passed up some supposedly better amps, which I could've easily gotten. But I haven't found any that has the portability, power, battery life, sound quality, and a euphoric bass boost switch all in one package. Even without using the bass boost on the c5, it had higher highs and definitely lower lows than what the internal amps on the x3/5 could put out. On the flip side, I have never found a sub $1000 dap that had a super great internal amp. Oh BTW, this is one expensive hobby.
Edited by chengsta - 6/16/14 at 10:12pm