Generally Japanese cards have a higher pull rate, yes, though it's also a more
consistent pull rate, which is much more important. Here's a breakdown:
- C - Common. Same as in English
- U - Uncommon. Same as in English
- R - Rare Holo. Unlike English cards, Japanese R cards are always holo.
- RR - Double Rare. EX, M-EX, and BREAK cards are all RR rarity.
- SR - Secret Rare. In BW/XY era, this is the rarity assigned to FA cards.
- UR - Ultra Rare. In the BW/XY era, this rarity is given to all secret cards that are not regular FAs, so things like the gold-bordered trainers, shiny Pokémon, etc.
In the BW/XY era of Pokémon, booster boxes come with 20 packs, and each pack has 5 cards. Each pack has a 50/50 chance of having either 3 C cards and 2 U cards, or 3 C cards, 1 U card, and 1 R/RR/SR/UR card. So, in one box, you get 10 R or better cards, generally 5-6 regular holos and 4-5 R/RR/SR/UR, though you get a maximum of 1 SR or UR per box. Chances of pulling an SR or UR are approximately 1 in 2 boxes.
As such, you get more holos and EXes or better than you do in English on average, and you also end up with less bulk C/U cards because the packs are smaller. And, best of all, NO NON-HOLO RARES. Most of those are U cards in Japanese. The downside is that SR/UR cards are a bit rarer, though, as are trainers (though of course Japanese structured decks are a better source of good trainers than English decks), which means they are more valuable in general. Of course, boxes are also significantly cheaper than English boxes (one booster box on AmiAmi costs about US€25), so you can buy 3-4 Japanese boxes for the cost of a single English booster box.
Another point worth mentioning is that Japanese cards have much higher production values than English cards. You won't see misprints or miscuts, and you won't have to worry about pulling cards right from a pack that already have scratches on them or other issues. In general, the cards are a much higher quality.
In terms of promos, Japanese Pokémon has a lot more promo cards than English. Sometimes Japanese promo cards will get folded into an English set (Example: the recent Surfing Pikachu, Slowbro-EX, and M Slowbro-EX cards are promos in Japan but are getting put into the English Evolutions set), sometimes they will become English promos (Example: the
Garchomp/Salamance boxes coming out in November), and sometimes they are never released in English at all (Example: We can be practically certain that this card will never see an English release).
Sometimes these promos are relatively easy to get. The Slowbro promos, for example, are available in packs that are sold on AmiAmi. Other promos can often be purchased on eBay and the like, with prices dependent on how rare and/or difficult to obtain the promo is.