Yes I think Al or Scandium frames have generally bigger diameters than Ti. Also, their weld beads are usually fatter.
WAY fatter. As a rule, the thicker the tube wall, the larger the weld bead needs to be. Al tubes are almost without exception thicker that Ti or steel, hence the bigger weld beads (like 5mm vs 2-3mm).
Also, bare Ti has a "dirty gray" color to it, where Al is more neutral to gray-white.
SP
Bend, OR