比如說 vs. 譬如說

The first few times in Taiwan that I heard (what I thought was) 比如說 bǐ​rú​ shuō​, I wondered why 比 bǐ  sounded like pǐ.  I just chalked it up as the Taiwanese accent.

Then I came across it in writing, 譬如說 pì​rú​​ shuō​.  Woohoo, I was hearing a 'p' sound, but I was confused by the use of a different character.

I've compared them on MDBG ... same exact meaning. 

I've compared them on nciku ... 比如說 has 6 sentence examples, 譬如說 has 0.

I'm just assuming it's another one of those Taiwan/Mainland differences, but I'm curious if anyone has a better understanding of the difference.  Is 譬如說 used at all on the Mainland?

譬 means "metaphor, simile, example".
比 means "to compare, liken; comparison; than".

Changye, I need you to come back! :)