Desperado only sustains your current momentum; it doesn’t provide you with any. If your RP opponent is letting you have free archive runs or other cheap runs, he is either ICE-screwed or playing badly.
To keep RP’s assets down, you need lots of credits quickly, and repeatedly, and MO provides exactly that. If you have to let them have 2 more credits so you can take 8 this turn and kill multiple assets the next turn, so be it. If you have Desperado in addition to MO, all the better. The Magical Kate deck posted on these forums has both, and they work extremely well in tandem.
Whizzard is another story entirely, which I won’t go into, but his ability is obviously very effective in the match-up.
My RP deck went undefeated in my local Regionals, and 4 out of 7 of those games were against Desperado Andromeda. None of them were any trouble, that day or any other day. Later that week I played 2 games against Opus decks and got absolutely obliterated because I could not keep an asset alive for more than 2 turns.