Cantonese is unusual. It's seldom written down. Standard Chinese (i.e. the written form of Mandarin) is used instead. So there are two comparisons.

Spoken Cantonese + Yale vs. spoken Japanese + Romaji.

Unlike Japanese, Cantonese has a very simple grammar and no registers (correction: honorifics), so it would be easier to learn to speak.

Spoken Cantonese + Written Chinese vs. spoken Japanese + Kanji + Kana.

Japanese script is less effort to learn, as it uses "only" 2000 Kanji. There's no such hard limit on the number of Hanzi you need. (But there's the complication of On-yomi and kun-yomi pronunciations of the same kanji.)

The other issue is the quality and quantity of learning material. Japanese wins by a country mile.