Microcosmic circulation is a very powerful practice to jump-start one's internal martial art practice, deep meditation and "longevity" program. But is it the only way? Recently I came across a little book called Tai-JiChuan Nei-Gung practice method (太極拳内功修練法) by a lineage Yang-style Master Wei ShuRen (魏樹人). Master Wei used a lot of Taoist meditation terminology and his practice resembled Taoist meditation in many respects. Yet, he doesn't do microcosmic circulation in his Nei-Gung practice!
What does he do? Firstly he focuses on Middle Dantian (which is rightly so for martial art practitioners). And then he circulates his chi down the inner thighs then coming up by the side. After chi comes up to the pelvis area, he will direct his chi to move along the side of his body, together with his middle Dantian focus. He then joins this chi at his head, and finally he allows his concentrated chi to flow en-route his eyes and back to his middle Dantian in a diffused manner. His chi thus runs along acupuncture routes, or chi-channels, but not Ren and Du single-mindedly like doing microcosmic circulation.
One thing of interest is that Yang style practitioners usually won't work with chi-channels so explicitly. Anyway Master Wei's instruction in his circulation does make good sense (and I shall go over his other instructions in some future day).
One similar practice comes to my mind, and it is the "forbidden" Fa LunGong (法輪功). Master Li might be quite "eclectic" in his spiritual approach, his chi-manipulation methods do make singular good sense. One of his methods is called Whole-body circulation (全身周天). And it is quite similar to Master Wei's. One key difference is that Wei's chi moves on the side up while Li's chi moves on left-right back up. The down route after the head though is the same.
Different chi practices can be quite similar, if one puts in an effort to try and analyze them: without any preconception about "which is better than which".