Sectional gutters are sold in pieces and installed as component systems.
Seamless gutters are considered more durable because the seams of sectional gutters can weaken over time and cause leaks 10 or 15 years down the road. This is because constant expansion and contraction of the gutters tends to crack the seam caulk of sectional systems. In this case the seams have to be re-caulked from the inside with a special gutter caulk.
We use the thickest material for our gutters with a wide variety of colors . I buy direct from the suppliers so you get an advantage of choosing from a hand full of samples which include over 30 plus color selections.