Esperanto is very regular, and this is considered good by some and bad by others. It can make parsing an Esperanto text simpler, because all nouns end in -o, all adjectives in -a, all adverbs in -e; plurals are formed by appending -j, and accusatives by adding -n; verb infinitives end in -i, and are changed to past, present, future by replacing the -i with -is, -as, -os. And you can make words from other words by compounding them or changing the ending for a different part of speech. When words were pulled into the vocabulary from natural languages they often had to be modified (deformed, some say) to fit the pattern, so words which should be recognizable sometimes aren't.
Occidental took a different approach. It tried to change the words as little as possible. It is regular, but regular in a different, slightly more complicated way. (A wise guy once said that anything is regular, if the rules are complicated enough.) Consider letters and their sounds. In Esperanto, every letter has one sound, and every sound one letter, with no exceptions. Very regular. I like this idea, but... familiar words had to be modified in ways that often make them unfamiliar. And most people, at least initially, have to make a conscious effort to pronounce those letters consistently. In Occidental, a letter may represent more than one sound, but it does so in a regular fashion that is consistent with the way that it is used in most major languages that use the Latin alphabet, and is based upon the way that sounds are modified by their neighbors. And although there is thus an extra rule to learn, it is usually not necessary to think about it explicitly if you're familiar with a Romance language, for these sound changes are characteristic of those languages. For example:
C before e, i, y as 'TS'; elsewhere as 'K'... centre, reciver, concert, acceptar, electric, electricita'
G before e, i, y, 'soft'; elsewhere 'hard'... gage, gigant, garage, gimnastica, guvernar, grisi, suggestion, magnific
If you try reading these words, I bet you'll find that in most cases, if you're familiar with a Romance language (except French, in which all bets are off anyway) or English (which has absorbed a lot of Romance), you automatically apply those extra rules without even thinking about them. And the extra rules are themselves regular.
I find Occidental much easier to read than Esperanto, for those new to the language. Don't get me wrong; I still like Esperanto and it's the auxiliary language that I know best. But it took me a long time to become comfortable with Esperanto, whereas I could read most Occidental at once. (Writing... well, that's another story. Esperanto is probably easier to write. And for the experienced user, it probably doesn't matter either way.)