For a 5 limbed shell type transformer and 3 phase bank transformer draw backs in (Y-Y) connection are same. So, are their constructions nearly same.
In transformer manufacturing, important is economy with quality. For five limb shell type, manufacturing cost would be cheaper than three phase bank type transformer, as the costly core material(M2H,N3H,M4 grade CRGO) needed for core would be less for same rating of three phase bank transformer, with less manufacturing (cutting of stamping, laboure & wastage) cost. Shell type, three phase auto transformer(stap down), will save considerable cooper too. For constructional details can refer the, design and manufacturing books for electrical machines or transformer, from library or can find from web.
A 3-phase core type (3 limb) transformer will be cheaper to manufacture than a shell type transformer.