There is no "one lens fits all" with T/S lenses.
For landscape and architecture, I use both a 24 and 85 t/s and occasionally my old 35 shift. It all depends on what works for my vision. I also use a modified TC 14e for the T/S lenses to give me more options.
Since I'm shooting both FX and DX, each gives me another option.
In the studio shooting still life, the 85 T/S works well and gives me lots of working room for lighting. In the field the 24 T/S is great and as a bonus, allows stitching of wider and taller subjects, but don't discount the 85 for landscape since this gives you increased DOF using the tilt and subject isolation for panos.
As for portraiture, the 85 T/S could be used if you have a fairly calm and not fidgeting subject, especially if you are using tilt for creativity. Since I'm running the original 85 T/S, it's fairly slow and awkward to shoot other than on a tripod and with very slow or stationary subjects.
In the field, the 24 T/S works well hand-held with the electronic aperture actuation. If I'm in a cut-and-run situation, I can run either a quick pano or shift for geometry without a tripod, though it's still best to do this deliberately with a level and tripod. Better to have the shot a little off than without one!
Of course this take a little practice!
Best bet to see what works for you is to examine which focal lengths work best for your vision then why not rent one for a week or two to see if one will work for you.
