I'm in a rush so this isn't as organized as I'd like!
They are both great carriers. The Pikkolo is much better for infants, since it doesn't require the infant insert, which I personally find awkward. If your child is very much into forward facing out, the Pikkolo is an obvious choice. It doesn't have a padded waistband (although you can get one as a separate accessory), so that makes the Pikkolo more flexible in terms of the types of carries. If you use it with the support belt, you can make the carrier body much longer than the ERGOs. Some people with leaners find that the body of the ERGO is too short once their kids are older.
The ERGO is slightly easier to figure out at first, the Pikkolo has more of a learning curve. The chest strap on the ERGO is attached, which I prefer. I also love the pocket on the body of the ERGO - it's so handy! Although you can use an ERGO front pouch with a Pikkolo and that's pretty much the same idea.
The Pikkolo can be worn with crossed straps while the ERGO really can't. I like crossed straps for a back carry.
If you are still wondering, why not order both from a company that takes returns - that way you can try them out and return the one you don't need.
Laurel
Owner, Carry Me Away
Mama to Jack, 5 and Maddy, 3