the hf2 is android/winphone/anythingbutiphone the hf3 is iphone only(both will work as headphones but the buttons wont work, apple decided they had to be different and swap a pair of wires so you wouldnt be able to use headsets from/for non-apple products and actually get full features..
i wish somebody would bring out a set with a switch in the control u could just slide over to change between phone types...
or that phones would all auto sense like a hand full of windows and android phones can, and actually work with apple headphones and have the controls work.
anyway, wear the cable over your ears, it takes a bit to get use to but, it fixes that problem fully and makes them stay in alot better to, i wish they would make a version shaped like the PL50 honestly, would make them alot easier to wear in bed, and the shapes designed to wear over ear....(they are the most comfy iem's you will ever find if you try some decent tips...like sony hybrids, shure, and even ETY tips...(lostearbuds on ebay, check him out for a WIDE tip selection at very good prices with an excellent rep ;) )
anyway, yeah, i like the hf5's, but, personally if im gonna trade mine in, im gonna get the er4pt, sure they cost a decent bit more but, they also have longer warr, replaceable cables, and are and have been the ETY flagship since the 70's, and are still one of the best iem's on the market, bar none...i have even considered grabbing a set of ety kids and using my e3 or e5 amp with them, im told they sound great once you amp them..(cheapest ety, dynamic with like 300ohm resistance....) since i could use them and then trade them in for the upgrade discount, without waiting for these hf5's to die....(rma'd them once because one driver died, then once on the other set i had when it died at the 3.5 jack strain relief, both times ety replaced them and tossed in a new set or 2 of small tri flanges...if you rma just make sure to request the size of tips you would like, they rep even said she would have sent me a little baggie kit of various tips so i could try them, i kinda would like to try their small foamies...but either way....i like ety, sure i had a couple fails, but the first one was within days of getting them, the 2nd was caused by leaving them plugged into the player in my pocket all the time, stopped doing that and havent had a set of any iem's fail at the plug since...i ended up with 2 because amazon messed up my order 3 times, and eventually in all the back and forth, they sent me an extra set of the color i wanted that they went out of stock on....(i ended up with black when i wanted blue, now i have both..but the other set are still brand new in their baggie i tested them for a couple hours and then put them back and went back to the set i have been carrying around daily for years now...)
i do recommend heading over to amazon and looking up sets of tips for ETY Shure and Klipsch you will find some kits of dif types/styles of tips for reasonable prices, i actually find the 3rd party tri-flange cut down to a dual flange(remove largest flange) to be most comfortable and isolating for me...(the 3rd flange for me and 3 friends just ends up wrinkling and causing discomfort rather then better isolation...)
the fact ety stand behind their products, and even replaced a friends set after the nozel broke off as he tried to pull the tip off to swap it with some comply foamies he had gotten...and admitted to them and everybody it was probably his fault for not being more careful....they replaced them no extra cost and even tossed him a full retail box replacement because they didnt have any ziplock bag replacements in stock at the moment...(that impressed me...they sent me extra filters and an extra tool each time though..without me asking funny enough..)