Ironically I was in the same boat comparing these two beasts. What made up my mind was the three following factors.
1. When you look at who is using what in terms of numbers their are many more world wide i30 users.
2. It is easier in live performance situations to use an i30 and get to another style immediately. It is also easier to change on the fly with an i30 as well.
3. This is just a personal opinion but I believe the i30 sounds are better and more crisp.. I also believe the add on abilities for new styles and arrangments are greater with the i30. The hard drive option is also a very nice feature.
One last thing to consider, when I have called different music stores all across the USA and have talked with people who are not bias to korg or Roland (In other words they are distributors for both) in almost every instance every salesperson and musician alike has recommedned the i30 over the g1000.