Okay, so it's been a while since I watched the show, but I seem to remember during Leland's confession he said that *HE* killed laura to protect her from being taken by BOB. but in the movie it seems that BOB was in control of the murder/loving every minute of it. I thought BOB would have wanted laura alive so that he could possess her?
shareFirst off, the movie definitely complicates Leland's relationship to Bob (which was complicated at times on the show but very much given a straight-up possession angle in the episode where Leland dies). It becomes less a matter of Leland being merely some unwilling vessel, and much more about a personification of his dark side, or rather an evil spirit which he is in some ways responsible for harboring. The film also shows us Leland - seemingly operating under his "own" judgment - sleeping with and later killing Teresa Banks, so it's no longer a matter of Leland only doing bad things when Bob is in the driver's seat.
Another thing: the scene in the film changed between conception and completion. The ring is not featured in screenplay (definitely not in the murder scene, perhaps not even in the whole film though I'm not 100% sure about that). Laura simply demands Leland/Bob kill her because she won't let Bob in, and that's what they do. In the finished film of course, Laura gets the ring from the one-armed man, puts it on, and THAT's what forces her murder. It's an action she's taken that somehow threatens Bob and/or exposes Leland (it was Teresa's after all, at one point). I've even heard speculation that the ring footage was added in post-production (with pick-up shots and some trick editing), and not actually part of the scene as shot; either way, it was a very last-minute addition, presumably because Lynch wanted the passive protagonist to take some sort of charge of her own fate at the climax. But this fact also reminds us how much the story and even meaning of Twin Peaks was reinvented/reframed as it went along.
In my opinion, the best way to look at Twin Peaks - series, film, even spin-offs like the Diary (which I view as absolutely essential in the development of Laura Palmer's character) - is as an evolution rather than a straightforward revelation of something already existent. Frost and Lynch say that Leland was always going to be the killer, and Frost at least has said there was always going to be a supernatural element although the form it would take was uncertain initially (of course Lynch's brilliantly improvised incorporation of set dresser Frank Silva birthed Bob). They didn't plan to unveil much about her murder for several seasons, but when audiences, critics, and the network put he pressure on, they had to wing it and scramble to assemble a satisfactory solution incorporating ideas they were just figuring out themselves. Compounding this, Lynch's and Frost's (but especially Lynch's) involvement with the show was sporadic at this point. While Lynch almost certainly conceived Cooper's incantation of the Tibetan Book of the Dead (Ray Wise recalls Lynch telling him about it when he broke the news that Leland was the killer, and it does have Lynch's fingerprints all over it), it's worth noting that Lynch neither wrote nor directed the episode. So it's hard to know to what extent he invented/endorsed the notion of Leland as a helpless vehicle which the episode emphasizes numerous times. Whether or not he was onboard with it, it feels very much like an attempt to soften the shocking blow of Leland being the killer (up till now the show has been emphasizing the lurid details of Laura's sex life but as soon as it's clear her father was behind it backs off the emphasis, as if uncomfortable). One line of dialogue is particularly telling: Truman says he has trouble accepting demonic possession as an explanation, and Cooper says, "Is it any easier to believe Leland raped and murdered his own daughter?"
I remember watching the show the first time and cringing when Leland was revealed, precisely for that reason. It seemed to fundamentally alter the show's tone and mood up to that point, upsetting the balance between tragedy, horror, comedy, and mystery. You can see the writers trying to compensate for this in the abysmal middle stretch of season 2 where they overemphasize the goofiness and ignore the darkness (even, perhaps especially, in the scenes at Leland's wake). But Pandora's box has now been opened and it takes the film to full deal with what has been released. As such, it's no wonder the account in the series and the film are not entirely complementary.
Finally, it's worth remembering that Twin Peaks marks a remarkable turning point in Lynch's oeuvre. All of his previous works had featured a fairly straightforward division of good and bad, safe and dangerous, light and dark. All of his subsequent works would blur this line and locate both of these qualities WITHIN individuals. Leland/Bob is the first time we see this process take place so it's no wonder that initially, even as the good and bad inhabit the same body, the division between them is drawn more sharply. By the time of Fire Walk With Me the groundwork has been prepared to acknowledge the evil side of a beloved character - and to identify with the victim instead of a heroic rescuer. It's fascinating to witness this process take place over 2 1/2 years but does make for some inconsistencies.
http://thedancingimage.blogspot.com/
Btw, that's a very long answer and not directly addressing your question. Short version: I think Bob wants Laura, but taking and wearing the ring denies him entry.
There's an interesting blog post exploring this issue, from the editor of the fanzine Wrapped in Plastic: http://abovethestore.blogspot.com/2009/06/subject-of-laura-palmer.html
http://thedancingimage.blogspot.com/