it's your call no doubt, but if I were you i'd go OFW on a ps3 slim. Slim ps3's were built so people could stop complaining overall.
if you really want a cfw ps3, get one of the original launch models that way when you hack it, it can potentially live up to "it only does everything" when you jailbreak it. i'm assuming that you want to play games offline? Well slim ps3 lacks proper backwards compatibility, even with hacks, so you miss out on pretty much an entire generation of great games.
you will never be back on PSN regardless of what CFW method that you use, so you won't get banned unless you break the TOS on PSN. your only hope to get online with a CFW ps3 is to sign up for xlink kai and play the games with LAN capabilities with others doing the same.
either way phat cfw ps3 > slim cfw ps3, so just go OFW so you won't have to worry about dongle teams sneaking malware on your PS3 when you try to bootleg newer games on it