When playing a physical copy of Suikoden on an actual PlayStation console, upon completing the game and your data is saved to a physical memory card, the data can be loaded into a Suikoden II game. This gave you certain bonuses such as:
• Starting Levels
• Starting weapon Levels
• Starting Equipment
• Dialog Changes
This can be done with the RGR Plugin. You'll need to rename your save files located in your RGR Plugin Data folder.
The file path for that is:

Windows 8, 7, Vista - C:ProgramDataVizzedVizzedRgrPluginUser-*****Mednafen_newsav
Windows XP - C:Documents and SettingsAll UsersApplication DataVizzedVizzedRgrPluginUser-*****Mednafen_newsav
Or go to:
Start Menu > All Programs > Vizzed Retro Game Room > Open Plugin Data Folder > User-***** > Mednafen_new > sav

(replace ***** with your user id)
You'd rename the save file 'Suikoden (USA) (v1.1)'.
You'll see 2 files:
• Suikoden (USA) (v1.1).4419082bad861064c26bfb0dec67aa6c.0.mcr
• Suikoden (USA) (v1.1).4419082bad861064c26bfb0dec67aa6c.1.mcr
Rename those to:
• Suikoden II.6fd9638ea372b47aa9a776ea8c528a2f.0.mcr
• Suikoden II.6fd9638ea372b47aa9a776ea8c528a2f.1.mcr
(if you already have suikoden II save files, you'll have to either delete them or move them to a different location on your computer before you can rename the suikoden 1 files to the suikoden II name)

tRIUNE : Just so you're aware, I don't think the starting levels, weapon levels and equipment are effected by transferring saved data. To the best of my knowledge (I've played and beat the game several different times) you can get different bonuses:
-Arriving in Banner Village shows Gremio and McDohl fishing on the far right side. McDohl becomes an available character after one of the Banner Village children are kidnapped and taken into the forest. This is only happens after you've reached Toran to forge an alliance and have recruited either Valeria or Kasumi.
-Dialogue Changes throughout the game. These are generally in reference to McDohl and whether or not he is in your party.
- Possible changes at the end of the game when you see where characters end up after the game ends.
I have not seen any changes in Starting Level / Weapon Levels or Starting Equipment with transferred data.
Please keep in mind that what I'm stating here is in reference to the actual physical copy of the Play Station games and these discs played on my Play Station 2. I've played the game with and without transferred data. I'm unaware of any other major changes but I do like to use McDohl because he's extremely powerful and he has a great unite with the main character of Suikoden 2.
I don't recall if I referenced any of this in my Game Guide.

Always on top of things. Thanks for this info, man. This is awesome!

Fireproof : I haven't completed Suikoden yet (although I've been meaning to if I ever have the time to; I first played it about 11 years ago through a rental from a local video rental store. That being said, I have no personal experience of transferring the data, but I knew that it could be done so I looked it up and found the info about the bonuses on this page:
//www.suikosource.com/games/gs2/guides/bonuses.php
I can take your word for it as I did theirs.

tRIUNE : Ohhhh I see now. Suikosource is a pretty impressive resource to use for information on Suikoden and it's a great place to discover a number of unknown things. I never actually saw the page you found your information from and if it's in Suikosource, it's legitimate. If you play Suikoden 1 and complete the game without Gremio and transfer the data, you will not find Gremio and McDohl in Banner Village, instead it's pretty much empty. I knew that without the 100% version of the data, you were not getting anything special other than McDohl to appear and become a character after a certain point in the game.
With that in mind, I never noticed the increase in character level on Suikoden 2 because it's near impossible to level up characters after a certain level, which makes it difficult to increase levels because earned Exp drops to 5 gained. I never noticed transferred runes or increase of weapon level either. For the most part, I've used many of the same characters to complete the game in 1 (Some are mandatory). With that said, their levels generally reached 60 before I slayed the final boss.
I did learn of a trick on Suikoden 1 where you can earn a massive amount of experience and boost some characters up to 60 levels. This was found through Suikosource (Very dedicated gamers). It requires you to take on 6 enemies in Moravia Castle I believe with just the main character and any character less than level 36. This gives you the maximum possible Experience so you earn many levels. Characters obtained at higher than level 35 earn less exp which could get them to level 80+ and you would need to continue to grind out experience to get to level 99.
You can play Jasper's Chinchinorin (3 Dice Cup Game) for unlimited money with a party with high luck! This is the best way to get the money you need to upgrade all weapons you like. You could fight enemies, which you might anyway but this is potentially the fastest method, especially if characters are already in the 90s.
Great post tho tRIUNE. I recommend you play and finish the game, it's worth it!