I bought a mini Space Case a few months ago and no regrets there... except I lost the little plastic scraper dealy that comes with it. Around the same time, one of my friends (a jackass) jacked a kief box from one of the headshops. He never uses it because, like you said, you have to grind manually to get as much kief as a grinder.
I have both, and I rarely if ever use my kief box. Only if I have some really nice buds that I don't want to go shredding up. Never knew they came with a scraper tool though, bought mine from a friend. That sure would be handy to have.
Keif collection is not about grinding. Keif boxes work best because the screens are made from silkscreen, this allows only the crystals (or resin glands) to fall threw the screen and onto the lucite where it is then collected. The grinders on the other hand grind the bud so fine that it too falls threw what is usually a metal screen. Metal screens have wider mesh and because you are grinding the plant material it is falling into the bottom along with the keif.
In essence, keif collected from a silkscreen keif box is more "pure" THC because it does not contain alot of ground up plant matter. It presses more easily and tastes alot better too.
I have both a spacecase grinder and a keif box. The spacecase is great because you collect alot of keif in a short period of time (I've ground up about an ounce of buds before in my spacecase and got around 3-5g of keif. The keif box I mostly use for storing my buds and collecting the keif after longer periods of time. Usually shaking the keif box yields more keif. A spacecase is a wise investment especially if you buy the little hash press from spacecase as well. I just made a nice little 2g chunk of hash from it from keif I collected over the past month or so from various different buds and it does deffiently knock you on your ass. As for a keif box if you have the money a Wicca box is the way to go.
And as for the little scraper thingy I found using one of those cheap plastic bristle paintbrushes works alot better as the keif generally does not really stick to the bristles.
Go with a space case for convienence and higher yields. A keif box is good for only really when dealing with large ammounts of cannabis though there are smaller ones. I had the space case first then the kief box so that in my opinion is the way to go. Kief box is also good for showing off pure class when sitting at home with some people over and you pull out this wooden box with some fine smelling herb in it.
A few days ago, I ordered a space case. I received it today, and find it to be the best service, highest quality and great value at a great price. It far exceded my expectations.
Also, its great to know that there are still some very good places to do online business with. One of my holiday presents to myself. Why did I wait so long?