In my opinion, it is MUCH easier to RNG for a WonderCard on HG/SS than on Platinum (and D/P is even worse than Platinum since it doesn't consistently hit strictly odd or strictly even delays). The main reason for this is that due to the lack of moving NPCs in the Cerulean Mart, you can safely verify your seed before having to advance the frame and collect your Pokémon. You can do this with the roamer method. Save in the Cerulean City Poké Mart (taking note of the location of the roamers upon saving), load the game, and check the map. Since there are no moving NPCs in there, you don't need to rush. You'll instantly know if you've hit your seed. If you wanted to check your seed first thing in D/P/Pt, you'd have to load the game, tap the Coin Flip app ASAP, open the menu ASAP to keep the NPC from moving while you await the result of the coin, close the menu and tap the Coin Flip app ASAP, open the menu ASAP as the second coin flips, etc., which is a pain, and there is certainly a chance that the NPC will begin to move during one of those very short periods of time spent outside of the menu. Instead of doing this, most people cause the Journal to auto-appear when loading the game, and perform the necessary number of page flips every single time they load the game. After closing the Journal, they talk to the delivery man ASAP to collect the Pokémon, and THEN they check to see if they got their desired result, either by examining the Pokémon's stats or using the Coin Flip app. If you're aiming for a high frame, having to advance it on every single attempt is VERY time-consuming, and with HG/SS, you only have to advance the frame if you know you have in fact hit your seed. Remember that even once you DO hit your seed, there's only a 1/25 chance that you'll get the right nature (assuming you're only looking for 1 specific nature), so it will usually take a very long time either way.
BTW, I made a post about WonderCard PIDs in the RNG Research thread if anyone is interested.
