OGXI also has a lot more downside - so if you do a risk/reward analysis you need to determine how much downside there MAY be between now and then as well as if its a "disapointing" deal whats the downside.
If you only consider the upside it looks like OGXI may be a better trade. But risk adjusted our #'s show ISIS is a much better trade. (cant look at just market cap - adjust them for net cash) if you subtract out the cash from ISIS it's got a $350m "enterprise value" dilluted
OGXI has a $200m dilluted market cap when adjusted for cash - so the #'s arent quite different 200m vs 400m
so its not 3% vs 40% its more like 8% vs 30% - peopel that missed OGXI if it does run will clammor into ISIS