I've used the RE-ZERO, DBA-02, RE0, and PFE but not the HF5, although I've used the ER4S. My understanding is the HF5 is a modernized looking version of the ER4 using the same drivers but is a little cheaper but not as guaranteed in frequency response balance between the left and right sides like the ER4.
I personally like the RE-ZERO a lot. For $99, it's excellently balanced, natural, and with a good life-like sound. They are a little forward but likable. Dynamics, texture, impact, tonality, etc. are all quite good for it's price point. It has a pretty natural sense of sound.
The DBA-02 is quick and aggressive. The treble energy is quite strong and a little forward due to mild dynamic breadth. The low end, to my ears and frequency response testing, is a little lean and does roll off a bit early but gradually. The speed and level of detail is impressive, but the aggressiveness of the treble might be off-putting if you don't want it, although the frequency response through the high end is ruler flat which is very nice. Personal preference, I wish the low frequency driver was as aggressive and offered the same presence as the high end but the low frequency driver is relatively short in decay and subsequently lean sounding. The presentation would be better balanced and fuller with a different driver.
The RE0 in some ways was like the DBA-02 but darker in signature. It too is quite fast and small on dynamic range. The RE0 driver requires a good bit of amperage. The sound is tighter than the RE-ZERO, not as open or effortless, and the low dynamic range does have the RE0 suffering from a less defined sound stage. The RE0 sounds quicker, sharper, but less effortless and not as dynamic. The frequency response is more broad than the RE-ZERO but not as balanced. I was not a fan of the RE0, but I do like what the RE-ZERO offers. I think it fixed a lot of key shortcomings of the RE0. I often recommend simply buying the RE-ZERO over the RE0.
The PFE is a very analytical BA earphone. It has a classic BA sound signature, very clean, short on decay, highly detailed, quick. It's also extremely dynamic, more so than many other earphones. The only step up in regard to dynamics is the SE530 which in some ways is a more refined PFE although the response and presentation is a bit different between the two. How they present the notes are similar though, more so than versus many of the other BA based earphones. The sound of the PFE is super clean, very detailed, and quite effortless. It's a very good earphone. It's like a more fun version of the ER4 but with a cleaner, shorter not giving up thickness, texture, and presence. The ER4 and subsequenty the HF5 will be a heartier, more textured note than the PFE. I like texture as it often carries a lot of smaller details within the music. Not having it sucks out some of the life and realism from the sound. The dynamics and cleanliness of note of the PFE are incredibly good, but the note is almost too clean. I would lean you more torwards the HF5 in this case to give you that more robust note, texture, and presence. This offers a little more meat, substance to the sound and creates a more believable and life-like presentation.
I will toss in another earphone ,the Klipsch Custom 3. This is another BA based earphone, in this case a dual driver earphone versus the single driver HF5 and PFE. Pricing has been within the $100 range, although it's been discontinued for over a year and is hard to find and find cheap. The Custom 1 and Custom 2 that Klipsch sold were largely junk, and I don't think people really noticed the Custom 3. Also the cord on these earphones suck. It's a thin cord covered by a fiber sheath that tangles super easy. It's very light though and doesn't really carry microphonics which is nice. People tend to use it till the cord fails and then convert then to cheap customs (custom mold customs) to which they are a great candidate for. The sound quality is very good, excellent note thickness, texture, dynamics, level of detail. Relative to other BA earphones, the notes are thick, but from a general standpoint, they're well bodied and convey a lot of information. The earphone is quiet well balanced in presentation. It does roll off a hair on both the bottom and top end but not enough to care and outpacing the single BA earphones anyways.
I often try to find earphones that offer a good balance of everything. I want the earphone to have a broad dynamic range, not too compressed. I want the earphone to be clean and quick but also thick and textured in note. I want the speed but also the presence. I want the earphone to be well balanced in response and presence offering a tonally neutral and natural sound. I want the frequency response to be well extended, not rolling off too much on the low end losing the deep bass and visceral sense nor losing too much up to and the air and sparkle of the highs. I like a good mix of everything. I feel the HF5, Custom 3, and RE-ZERO will all be good candidates. The others tend to suffer a bit in certain areas and detracts from the overall presentation somewhat. The others are good for certain reasons, but when we want the total package, we want as complete a package as possible. We essentially want the earphone to do everything well. It's hard to pick an actually best product because it depends on personal preference. All three offer a good mix of everything, but they each have their own sound signatures. From a personal preference standpoint, I would lean most heavily towards the Custom 3. The dual driver offers a little broader performance than the HF5 and offers a thicker, more energetic note. The HF5 is likely a litttle cleaner, brighter, but the Custom 3 offers a more filling presence. The RE-ZERO is very good though, excellently detailed, a little forwards but natural and with a life-like quality. It's not as energetic and articulate as the Custom 3 but a little more natural sounding. The HF5 will be the best built product and quite stylish. The RE-ZERO looks good but will feel a little cheaper. The Custom 3 is all plastic and with a thin cord. It feels less substantial and cheap. I personally like the very light weight of the cord, but the tangly nature is annoying. However, you can spend $100 and convert them to a nice set of custom molds later down the road, and it effectively becomes one of the cheapest dual driver custom earphones on the market. The RE-ZERO is a dynamic and will never be that, and there is little reason to go such a route with the HF5. The choice between the three will come down to personal preference.