VIP is basically the upgrade of tori prime, allows bigger avatar, bigger sig, at least used to give you access to the VIP Board which was basically wibbles but only for VIPs, etc
That's what I understood from various threads, but on the shop they are the same thing (see the picture). Unless I'm missing something, there isn't an option to buy Toriprime and then VIP.
ToriPrime was deprecated and ToriVIP was updated to Forum VIP. Forum VIP has all of the perks of ToriPrime and ToriVIP combined (excluding 5k TC globals, that was removed).