Vexillologically speaking, a flag should avoid placing “colors” against “metals” (i.e. “silver,” or white, and gold). Flags 3 and 4 violate this principle, to no clear advantage.
Flags should be reversible, so that one can silk-screen it rather than having to print the damned thing twice and sew it together. This means no writing, and no maps. Flags 3 - 6 violate this principle.
Flag number 2 is technically okay, but looks like it was designed by a color-blind elf. The central image would not symbolize much of anything for the vast majority of viewers, unless they confused it with the Ashokan pillar design (or is it Gandhi’s spinning wheel?) on India’s flag.
I have to say that with one exception, these flags are quite simply uninspired.
Furthermore, since several of the flags are already in use by certain political organizations, this discourages their adaptation for use as a national flag. (Yes, I know the KMT didn’t follow that principle particularly closely.) This means, for example, that the DPP flag would make in inappropriate national flag, since it could not unite the people beneath it.
Now the exception: Flag number 1, the Yellow Tiger Flag, is vexillologically as well as aesthetically beautiful. It features a bold central image which no other country uses (the current one looks too much like Burma’s), and which by happy coincidence would serve well as a symbol of Taiwan (one of the Asian “tigers”). I wish somebody would print these and sell them at rallies. I’d buy a bunch!
One problem is that it might appeal more to independence advocates than to pan-blue types, if that is a concern. Perhaps its promoters could remind everyone that its creators were anti-Japanese Ching loyalists.
Some temples have an image of a baby and mother tiger together. Perhaps that would be a suitable “correction” in the event that Taiwan becomes a Special Administrative Region! Placed in a blue jack, replacing the KMT sun? But the Chinese would probably prefer a blue-and-white plum blossom on a red field, on analogy with Hong Kong.