I am not sure about this as I havn't used one, but as I understand it, the lono2 from paradisearcade.com is a joystick encoder, not a keyboard encoder. Meaning that you have the 4 joysticks and their buttons, but I am not sure if the admin buttons, player start buttons, and coin buttons work from it. So if someone who knows about this and confirm whether the lono2 can handle these, or if the OP will still need another keyboard enocde in addition to handle those inputs.
As for my opinion on which to get...I would choose the ipac4, just for the fact that it is easy to setup, and the shipping from ultimarc is awesome. I get my stuff from the UK to my door step in Canada in 2 days.