Another chance to use imagination, I say. One of the reasons Solo chose the asteroid was because of the composition of the rock and the difficulty it gave sensors. Obviously, the Imp's didn't know his exact location as they were strafe bombing the asteroid - they were relying on visual recon of his last coordinates. So if the Imp's couldn't see the Falcon, the asteroid likewise blinded the Falcon. It was yet another calculated risk Solo took in that asteroid field.

Dagobah presented none of these issues for the X-Wing. The problem is not the ships or the scanners - it's got to be the environment. Where better to hide than a sensor blindspot?

Fair point Moose (although how do you know he chose that asteroid for the reasons you stated and not just because 1-it was a big enough hole to hide in and 2-it was the nearest and quickest place to hide out?)
Presumably (and that's always a dangerous phrase to use!) the four pursuing TIE's couldn't have been relaying their chase back to the Executor, or else they would have been on them quicker (Vader would have certainly sent TIE's down there, even if it meant probable destruction). Saying that, as soon as they leave the slug they are in a fight again with an ISD on their tail.

Very neat point about the string of calculated risks that Solo took - that's how he muddled through life, and why he's such an attractive character to watch/read etc.
A counter question then Moose - if it had been Luke going into the asteroid field, do you thik he would have sensed the Slug? Or don't you think his powers were acute enough by then.

Fair point Moose (although how do you know he chose that asteroid for the reasons you stated

I don't! :0) But if it could work that way, that's a start. It's also in character with Solo's actions - 1) firstly taking the chance to enter the field in the first place 2) looking for a blind spot to hide on Needa's Destroyer. He never tells everyone why he's going in closer to one of the big ones - and he doesn't necessarily know if there would be a large cave there either. There may have been another reason he was attracted to that asteroid. So, if it's in keeping with character, it works for me. It's not an official answer, just my own.

A counter question then Moose - if it had been Luke going into the asteroid field, do you thik he would have sensed the Slug? Or don't you think his powers were acute enough by then.

Good question - Luke seemed at that point only attuned to sensing people, especially people close to him (Vader, Leia, friends, etc). If he had sensed it, I wonder if he would even know what it was. Dunno.

i agree with moose the asteroid would have prevented the sensors of most ships. also theres the slight possiblity the x-wing has a better sensor than the falcon(the falcon being comprised of a lot of spare parts and what not).

He never tells everyone why he's going in closer to one of the big ones -
That's a very good point, although I always felt that when Leia and Threepio both exclaim "Closer!" Chewie is registering his agreement - after all, he more than anyone would be used to Solo's crazy stunts.

Two more reasons, hope you see these-

1)Solo wasn't expecting life forms, so he didn't check. Luke wanted to know what the planet would be like, so he checked.

2)Dagobah was positively teeming with life. One Space Slug and a few Mynocks? Hmmm...I dunno. in that asteroid, they probably wouldn't show up. Besides, to try to generate heat in a vaccum is to waste a major amount of energy, and do you really think a space slug gets enough food for that?