A static WAN IP from your ISP is easier. It will not change.
A dynamic WAN IP may change, thats where DDNS comes in. Do some reading about DDNS.
However, even with a static WAN IP, DDNS might be nice. Then remote vistors do not have to enter something as http:// 123.225.112.221 but an easier to remember URL, like
http://cecemf.no-ip.com.
About problems with PS3: This is about having a dynamic or static LAN-IP. LAN (L=local) is within your own network. With a static or dynamic WAN IP you can choose to set up your router with a dynamic or static LAN IP.
(WAN IP: your world wide unique address. LAN IP: the "room number" within your LAN, Local Area Network)
One last remark: Set your NAS to a static LAN IP. Even with a dynamic WAN IP, and a dynamic LAN IP, it will then still use the same LAN IP. Absolutely necessary if you want to forward a port in your router to your NAS.
DS412+. 1x WD20EFRX + 3x HD204UI, SHR (RAID5). DSM 4.2-3211.
DS210j. 2x HD203WI, RAID1. DSM 4.2-3211.
Router Netgear WNDR3700. Switch TP-Link TL-SG1008D. AcRyan Mini v1. UPS APC BE700G-GR. Ipcam Edimax IC-3010.