I've used pdfLaTeX for one year but I've got a specific issue and I'm considering switching to XeTeX or LuaTeX. I've seen several questions about pros and cons of each option but they don't really help me choose since they show cases where several texts, each in a different script, must be used:
I must type a document involving several languages and several scripts alternatively, meaning the script changes several times in the same sentence/paragraph, as in a multilingual dictionary (one word in English, then one word in Chinese, then one word in English again, then one word in Persian). The scripts involved are: latin, arabic, polytonic greek, cyrillic, chinese, japanese, devanagari and some others like ge'ez, korean, georgian, thai...
Using a WYSIWYG method I'd have been able to copy/paste many Unicode characters, but what would be the best TeX option, considering the effort involved:
to learn how to deal with a new system (XeTeX or LuaTeX),
to type my inputs (it is far easier to enter a transliteration to be displayed as another script in the pdf, than to copy/paste many Unicode characters),
to switch languages/scripts fast, easily and (very very) often, which is the major criterion?
Stay with pdfLaTeX-babel-arabtex-etc. (would the utf-8 encoding I use support that?), switch to XeTeX-polyglossia-arabxetex-etc., or switch to LuaTeX-I don't know what yet-etc.?