Both, U18t and Fourte? I think the main decision will come down to your sensitivity to treble and desire for more bass
From my Fourte review conclusion: "... I like the strong authoritative impact of U18 bass, but I also like the deeper analog texture of Fourte bass. I’m a fan of U18 smoother, resolving, natural upper mids and lower treble, but I also enjoyed Fourte with its more transparent, revealing, detailed mids/treble that wasn’t too fatiguing." You want more bass and smoother treble - U18t, leaner more revealing/analytical sound - Fourte.
I haven't listened to UE18+ Pro for awhile, need to refresh my "ears", so will look for it. UE18+ Pro was an upgrade to a neutrally tuned UERR, where it lifted the mid-bass and added more sparkle to treble, but it nowhere near the tuning quality of either U18t or Fourte.
But it all comes down to a personal preference. I'm obsessed now with Trio and its bass