They're the same. What little extra I might've paid by having to use OPC servicing I saved by not needing to mod the car, so it actually worked out cheaper.
15k a year means you'll be servicing once every 18 months, which isn't that bad at all. Gen2 engines can use a bit of oil though (by design), so take that into account. As a guide, mine used about 1L every 2500 miles.