This topic has been discussed before.
http://www.arcadecontrols.org/yabbse/index.php?board=1;action=display;threadid=14404;start=0
Now, if people can limit this to a civilized conversation we won't lock it.
Personally I think the new mini-pac is a better solution, unless you don't want a t-ball or spinner. Then it's a toss up.
Agreed, KeyWiz vs. I-PAC/2 has been debated extensively in the referenced thread.
The mini-pac is a different animal from the above, better in some ways, worse in others.
Here are my personal opinions on it:
Pro's:
No wires to strip and crimp.
Small board size.
36-input version will eventually be available (at same price).
Supports one trackball or two spinners.
Con's:
Will not work with the new WinIpac IPD software.
Wiring - Uses a pre-made harness or can use an IDE cable. IDE cables are hard to crimp to. The pre-made harness will possibly be too short (yes, you can use extension cables, but . . . ) or more likely too long (you can cut and put on a new terminal end, but then you're eliminating the reduction in effort of the pre-made harness). Also, the pre-made harness uses 1/4-inch terminals and most arcade controls use 3/16-inch (although some use 1/4-inch).
Wiring - With an I-PAC/2, you can move wires to a new terminal, with a mini-pac, you can swap switches, but if you've shortened wires as mentioned above, then it won't be a pretty mod.
Trackball/spinner support - The built-in support is basically half of an Opti-Pac, but it won't work with all trackballs (like the Opti-Pac will).
Cost - With a pre-made harness, the board is about the same price as an I-PAC/2, but you do get half of an opti-pac included.
Unknown: I'm not sure if the t-ball interface will auto-switch between spinners and t-ball like an opti-pac will. (I think it does, but didn't want to say one way or the other without knowing).
P.S. Sorry for taking the thread off-topic.