neither is better or worse than other and totally dependent on your specific toplogy. In general, if your output is connected to a capacitor, you want it to be a controlled current source, and if it is going into and inductor, you want a controlled voltage source. You can compensate by adding a snubber resistance if you need to connect a current source to an inductor, but this will likely require smaller time steps and slow your simulaiton down. In general, it would be better to use the simscape battery model instead of combining the two technologies. While the converter blocks allow it, it typically makes your simulation noticeably slower and actually decoulples the two electrical networks which does add a small innacuracy.