My 5Tp arrived today, all I can say at this stage is I very much look forward to them breaking in. side by side to the T70p which have several hundred hours on them and i'm not sure beyond a little detail what the 5Tp do better. They clearly need breaking in. Anyway, a journey is ahead and one I very much look forward to.
I had the same question and it took me two months to finaly conclude that the T5p do some things better than the T70p. I ended up keeping the T5p and sold the T70p. Mainly the comfort and quality of the materials and not the sound made me take that decision. I could easily live with the T70p. Both the T5p and T70p scale very well with better source and amplification. In fact T70 react better to crossfeed on the Meier Corda amps than the T5p so T70p do somthing with regards to soundstage that my ears cannot perceive with the T5p.
On the contrary to Arttt I belong to the belief that the charachteristics of the headphones do not change during break in of the drivers. If there is a change it is less than one can hear. I know based on years of shifting between headphones with dark or bright signatures, that getting used to a signature over some time, changes ones perception of the sound A LOT when you get used to more or less bass impact. Once you adjust to the lesser bass impact of the T5p/T70p you start to perceive the details and soundstage they have. It has been like that always and that is why people either love or hate Etymotic ER-4S, T70, HD800, T5p.... etc. and other headphones not having the elevated bass impact.
So my advice is to forget about break-in and start to enjoy and open you mind to the sound! I admit I do break-in myself using white noise, pink noise etc. but that is more to satisfy my psychoacoustic perception of the headphone/earphone. I believe that has better effect on the sound.
Also knowing this one can use it to choose which portable headphone to use in coorporation with the T5p. When I use the T51p which has a VERY impactful bass I enjoy the bass more when I am used to the T5p. When I am adjusting to the T51p for some days I enjoy the details and bright, airy sound of the T5p.