Here are all the differences I can think of (bear in mind I do not have a v4.5)
Games
v4: The games are Jumping Rope, Mimic, Shape, Dance and Flag.
v4.5: The games are Climb, Tug-o-war, Apple, Shapes and Manhole.
Characters
v4: Babies are Tsubutchi and Kuritchi (or male Tsubutchi- I call it Kuritchi because it looks exactly like a Kuritchi).
v4.5: Babies are the same as v4.
v4: Children are Harutchi, Puchitchi, Mizutamatchi and Mohitamatchi.
v4.5: Chilren are Hitodetchi, Kuribotchi, Tamatchi and Kuchitamatchi.
v4: Teenagers are Yangu Mametchi, Yangu Robotchi, Yangu Mimitchi, Ringotchi, Gurumetchi, Hinotamatchi, Ichigotchi, Yangu Memetchi, Yangu Kuchipatchi, Oniontchi, Yangu Dorotchi, Nikatchi, Hawainotchi, Hawaikotchi, Obotchi and Ojotchi.
v4.5: Teenagers are Ura Yangu Mametchi, Kurakkatchi, Zouritchi, Ura Yangu Marotchi, Daiyatchi, Kujakutchi, Ura Yangu Memetchi, Ura Yangu Furawatchi, Kometchi, Bokusatchi, Ura Yangu Yattatchi, Yakantchi, Hashitamatchi, Hikotchi, Ichigotchi and Yufotchi.
v4: Adults are Mametchi, Robotchi, Zukyutchi, Mimitchi, Meidotchi, Marotchi, Tosakatchi, Togetchi, Shimashimatchi, Ponitchi, Memetchi, Furawatchi, Minotchi, Tarakotchi, Kuchipatchi, Pukatchi, Sebiretchi, Yattatchi, Pyonchitchi, Debatchi, Gozarutchi, Pyonkotchi, Hanatchi, Masukutchi
v4.5: Adults are Uramametchi, Samuraitchi, Matsuritchi, Horoyotchi, Tsukkomitchi, Urazukyukotchi, Serebutchi, Yasaguretchi, Uratogetchi, Purimatchi, Uramemetchi, Urafurawatchi, Tenpatchi, Tougyutchi, Urakuchipatchi, Urayattatchi, Uradebatchi, Shitekitchi (nope that wasn't a typo), Mametchi, Kuchipatchi, Gozarutchi, Mimitchi, Memetchi and Furawatchi.
v4: Secret characters are Tensaitchi, Makiko and Nonbiritchi.
v4.5: Secret characters are Hyottokotchi, Hanagatatchi and Mukimukitchi.
v4: "Old-timer" characters are Otokitchi, Ojitchi and Oyajitchi.
v4.5: "Old-timer" characters are the same as v4.
Jobs
v4: Jobs are Chef, Scientist, Baker, Florist, Doctor, Banker, News Reader, Rock Star, Fashion Designer, Teacher, Fireman, Kindergarten Teacher, Amusement Park Worker, Tour Guide and Hairdresser.
v4.5: Jobs are (this is from an instruction booklet that I don't completely trust lol) Chef, Clown, Baker, Florist, Banker, Doctor, News Reporter, Rock Star, Teacher, Weight Puller, Fireman, Kindergarten Teacher, DJ, Tour Guide and Hairdresser.
Miscellaneous
v4: On the v4 growth chart from Bandai the characters are sorted out into "families." v4 characters stay within their family.
v4.5: On the v4.5 growth chart from Bandai the characters are not sorted out into "families" (though the characters do have families on the Uratama). v4.5 growths are erratic.
v4: Skill points are Intelligence (pencil), Style (star) and Kindness (flower).
v4.5: Skill points are Humour (face), Gorgeousness (sparkle) and Passion (fist).
