Once you have 300 reputation, you can create tags; so you're free to do so. You simply edit an appropriate question and type the name you want for your new tag in the tags field (supposing there aren't 5 tags already--that's the limit). If the tag doesn't end up on at least one more question within six months, it will be automatically deleted. For more information, see here.
Regarding the merits of this proposal, I personally don't have strong opinions. You've done the research, if there are recurring on-topic questions about this issue, then we should have a tag for them. Here are a couple of suggestions I have about tag creation:
- I think it would be better to have one tag than two.
- You can't have spaces between words, you have to put a dash "-".
- My guess is that 'tailed' is more common terminology than 'sided'.
- It's best for tags to have names that are as short as possible.
- If there are several names that might work almost as well, you could preempt them by asking the moderators to create them and make them synonyms of your new tag.
So a possible name might be:
[1-vs-2-tailed], but I'm sure someone else might be able to come up with a better name.