Heterogeneously coupled SK-SMLQuantum Dot (QD) heterostructures has superior characteristics compared to homogeneously coupled SK QDs in terms of dot density, cumulative strain and absorption efficiency. Here, we have carried out a comparative analysis between heterogeneously coupled SK on SML and SML on SK QDs heterostructures. The barrier thickness between SK and SML QDs, in both structures, has been varied as 5, 7.5 and 10 nm. The tunnelling of carriers from one type of QD (SK/SML) to another type of QD (SML/SK)has been explicated through photoluminescence (PL) study. The appearance of SML peak along with the SK peak for higher barrier thickness has been observed in case of SK on SML QD heterostructure. This might be due to decrease in tunnelling probability of carriers and thereby, transition takes place from both SK and SML QDs. However, this phenomenon has not been observed in SML on SK QD heterostructures. The reason might be the reduced average barrier thickness between SML and SK QDs, which allowed tunnelling of all the carriers. Thus, SML peak was absent in all three SML on SK QD heterostructures. Moreover, strain distribution in all the heterostructures have been investigated through high resolution X-ray diffraction (HRXRD) measurements. The significant modification in structural morphology of QDs, can be obtained fromHRXRD, clearly demonstrates variation in strain with respect to barrier thickness. This comparative analysis would help the research community to choose the optimized heterostructure for desired optoelectronic applications.