Rainbows Or Rummys?

[McCool]

Tank:
55 gallons.
Fluval Canister filter, rated for 65 gallons.
All live plants.
Sand.
Driftwood.
Very established.
Ammonia/Nitrite: 0
Nitrate: 30
pH: 7.5

Current Stock:
2 Angels
1 Betta
1 Whiptail Cat
4 Polka Dot Loaches
3 Swordtails

I'm looking to add a school. Originally I decided to go with Rummynoses. Then, I started remembering how much I love the Red Rainbow fish, and now I'm not sure. I can't remember the exact species of red Rainbows my LFS carries though. I think a school of atleast 6 Rainbows may be pushing it, However, I will say that my live plants keep my water very clean. My Nitrate is consistently 30, and that's with fairly sparse WCs. I was doing 50% a week, but then I started just watching my water and it would seem like I certainly don't need to do them as often. So, my question is, which do y'all think would work better? A larger school of Rummys, or a smaller school of Rainbows?
Here's a picture of my tank.

 

[Blondielovesfish]

I would personally go with Rummy noses as they seem tighter schoolers and by being able to have higher school numbers, you would see them more often than the red rainbows. 
But if you like the rainbows then go with them.

 

[TallTree01]

I would go with rainbows.
Get some more loaches too, they'll thank you for it.
Watch the angels and betta for aggression btw.

 

[clivealive]

we love rummy, my choice and do school well

 

[McCool]

I would go with rainbows.
Get some more loaches too, they'll thank you for it.
Watch the angels and betta for aggression btw.

Yeah, I've always wanted to up the loaches. I'll add two more.
No aggression between the two yet. My largest Angel is a huge wimp luckily. When I bought him he was getting picked on by angels not even half his size. I'll separate if I ever do see a problem though
Any idea of how many rainbows I could have?

I would personally go with Rummy noses as they seem tighter schoolers and by being able to have higher school numbers, you would see them more often than the red rainbows. 
But if you like the rainbows then go with them.

You've just wrapped my whole conflict up in one post! Rainbows are one of my favorites, and I've never been in a position to own them, However; I really wanted something small that would school like crazy!

Any idea on how many rummys you think I could have?

 

[TallTree01]

If you want to add as many rainbows as you could possibly without overstocking I would say ..... < drumroll > ......
8 plus the 2 extra loaches.

 

[McCool]

If you want to add as many rainbows as you could possibly without overstocking I would say ..... < drumroll > ......
8 plus the 2 extra loaches.

I think I'm pretty much sold on the rainbows Any idea of what I should do for M:F ratio?

 

[TallTree01]

Maybe 3 males 5 females?
Dunno hwo you'd tell though

Keep in mind this will be ahevy stoked tank so be sure to keep up with water changes.

 

[McCool]

Maybe 3 males 5 females?
Dunno hwo you'd tell though

Keep in mind this will be ahevy stoked tank so be sure to keep up with water changes.

Of course! The females really are colorless, but I know the males have to have females in order to really show off their color. Thanks for the help!