2011/3/3 Andre Engels <andreengels@gmail.com>
In the past the pywikibot output was indeed rather slow when there was
much to transliterate, but the problems on that point have already
been resolved in my edit #6275, from January 2009, when
transliteration was changed from a sequence of elifs to a dictionary.

You are right, I made an experiment. The above mentioned command was killed with ctrl C after 10 and a half hours, and has collected approx. 950 titles by that time. Now I commented showdiff out, but not the line pywikibot.output(page.title()). This time it collected 3200 titles in the first 24 minutes! So only showdiff must be switched off.
The question is: should we restrict this option to -always or -always -save?
P.s. The script finished in merely 43 minutes, and collected 4246 articles. This is MUCH faster than with showdiff on in Latin wikis, so showdiff is the brake anyway. I will never collect articles with -save and -showdiff again. This is a new world. :-)