I believe I already saw based on the footage that it was Warlords and not Onimusha, but we'll have to get our hands on the game to be sure. In terms of voices it depends on the region. Genma Onimusha had JPN audio in the USA and ASIA releases, but EU missed out. The voices are extremely horrible but they have a corny likeability to them.
Have to say I never thought this would happen due to the copyrights of the actors having expired and it being to expensive to renew. Really hopes this means we'll see the rest of the series too. While I liked Genma the most, there's some excellent games in there.
Capcom noted that with DMCV and RE2make they are noticing increased interest in older titles, hopefully this means we'll see them return in some shape or form.
Genma isn't that well known so that might be the reason, and most thought it was just 'a port' while it was much much more. That said putting "includes all the extras from Genma" would've only improved upon it.
To expand upon what Bird noted:
- Hard Mode added with a special rank you can gain only on that mode which requires absolute mastery;
- All armors are removed (which were recolors) with unique designs that have special stats like a Ninja Armor.
- There's a Green Orb system which is really fun and unique. Basically randomly when killing enemies a Green Orb will spawn and you have to 'fight' to absorb it. You cannot move or attack while 'fighting' for it. If you win, you get one in stock. If you have 5 stored you can expend them to become fully invincible and healed for a few seconds. While this seems overpowered its a really cool system that rewards planning one when to use it. If a foe (or boss) wins, they become super buffed. If you beat a buffed enemy however, they drop more XP. So if you want you can buff a boss/enemy and Issen them to death for massive XP gains.
- Evil Doll enemies, extremely powerful foes that are extremely hard to defeat for newcomers but give a ton of XP when beaten.
- Charge attacks. You can charge in 3 levels, each giving a different move with different properties and rewards (in terms of what orb type you receive). Some launch, some knock back etc.
- New areas.
- a complete subquest revolving around unlocking a tower that houses a miniature 'bloody palace' with a secret boss and powerful armor as reward.
- item locations remixed as well as new enemies and enemy placements.
- unique unlockable costumes.
- And the biggest one imo: allows you to skip cutscenes.
I'm not going to lie it is the definitive way to play the game.