I'm the same speedwell who originally answered this question, heh. I was pushed by a Singaporean colleague to sort this out, and they would not accept "forget it; they're both the same these days" as an answer. They were *interested*. So I spent some more time thinking about it, and I realised I do have an unconscious preference. (Oh, and I have code switched to British rules because I now live in Ireland.)

The difference is subtle but meaningful and has to do with *plausibility*. Imagine I were a chef in a restaurant, and I asked a server how a food critic liked the dish I cooked. They might say, with their thoughts in brackets:

- "Well, she ate it as if she liked it." (I am of the opinion that she liked it, since she ate it with enthusiasm.)
- "Well, she ate it as though she liked it." (I am of the opinion that she didn't, since it seemed like it was an effort for her to eat more than the first bite of it.)

In other words, I would lean toward "as if" if the conditional was plausible or likely, and "as though" if the conditional was implausible or unlikely or imaginary. A few more examples:

- I walked down Union Street as if Aberdeen was my new home. (I'm just a tourist, but it feels like a homecoming somehow.)
- I walked down Union Street as though Aberdeen were to be my new home. (I wanted to make myself look like a potential new resident, not just a tourist, but I'm not really going to live here.) Note the subjunctive, which, while dead as a dodo, is still used with "though" and not "if", as noted by others.

- The little Italian girl smiled as if she understood what I said. (She very well might speak a little English.)
- The little Italian girl smiled as though she understood what I said. (She didn't understand, but she was being sweet and polite.)