as someone who has almost stayed in both (i'm a swan girl!), i think that your decision really comes down to whether you want to spend the additional $$ for the dolphin...
when i stayed @ the safari, we got it for $35 a night (in dec) thru priceline. it was absolutely worth every single penny of that rate! the beds were extremely comfortable & the hotel itself is very nice. imo, is it worth $100+? probably not....but if you can get it at a discount rate, i always encourage ppl to go for it! i've never gotten it again at that rate, but when we stay offsite (or not at the universal hotels), i'm always keeping my fingers crossed for the safari!
i've stayed at the swan (& visited the dolphin) and i'm assuming their rooms are at least comparable....they too are extremely comfortable. i thought our room was spacious & it felt like a "deluxe" hotel. of course the disney perks (the free transportation & EMH) are always a good thing! i enjoyed the restaurants in the dolphin (shula's, the dolphin fountain, & tubbi's) but did think that the dolphin was a smidge too big for my taste...can feel a bit impersonal!
hope at least some of this was helpful! let us know what you decide!