Having raced a few SeaDoo's over the years, I can speak from experience. Quality oils will extend engine life. In particular, piston ring wear over the exhaust port area. Lower quality oils will not cause other issues with SeaDoo's. But the ring wear is a known issue.
Any EG-D oil is likely to be good enough. I tried many different oils in an attempt to reduce ring wear. Redline Racing Oil was not good due to corrosion issues. Golden Spectro worked quite well. As did the Factory oil. Mobil 1 MX2t (no longer in production) was the absolute best. Castrol TT-S also worked quite well.
As odd as it seems, the Bombardier oil was not more expensive when purchased by the gallon.