I'll make some generalizations, since I have not yet heard phonix, but my thoughts are based off my experience listening extensively to bird/erlky-2 (and phonix is indeed based on erlky-2.)
Listen for major differences in the overall thickness and closeness of the sound.
Traillii is relatively laid-back in its presentation; you are placed slightly farther back from the music. erlky-2/phonix is a much more in-your-face sound with an extremely thick and lush presentation. vocals on erlky-2/phonix (and ve iems in general) are filled with body and emotion, which to me is one of the most distinguishing characteristics of ve's house sound. Indeed, vocals on the bird are also very emotive, but presence comes more from micro-detail and texture vs the heft and weightiness that ve breathes into vocals and midrange.
Treble is a bit more subdued and "rounder" on erlky-2/phonix vs. traillii, but erlky-2 extends nicely to my ears. I am guessing treble will still likely be calmer on phonix vs. the estats on the bird, even though of course ve did focus on enhancing treble on the phonix. I am definitely curious to hear what ve did here.
Lastly, erlky-2 is far more mid-bass focused vs. sub-bass focused. I sometimes wish erlky-2 had more sub-bass (and am surprised that ve focused on enhancing the bass rather than the treble for the phonix.) that said, erlky-2 makes the best use of mid-bass I've ever heard and creates an extremely engaging, punchy, and fun sound. traillii has a solidly present midrange, but sub-bass is also extremely well done with great texture.
Again, this is all somewhat speculative since I haven't yet heard the phonix. I don't normally give impressions for what I haven't heard, however, considering phonix is based on erlky-2 with relatively minimal changes, I feel confident these impressions will still be at least somewhat relevant.
Looking forward to getting an ear on both the phonix and ext soon...