Some people prefer to edit on the computer. I personally prefer that they don't. Reason number one for me is that I sometimes enlist the help of people who are either very busy or have things they care much more about than my writing. Giving them a hard copy gives them more incentive to read it, especially because they can take it with them and get comfortable. I, for myself, like to edit on something printed out occasionally, so I tell my betas to write stuff down and manually edit if they see something that needs a good fix. It's easier for me to search and find if it's printed out.
I have one friend who told me she'd beta if I sent her the file with my actual story. The reason she wants it is because she wants to change things on the screen herself. She also proclaims that her theory is; if people don't spot her edits, she did a good job and the original wording is obviously not missed. She will not show or explain what she changed. By the time I'd give anything to her, I'm fairly confident I'd notice the slightest change in anything, because I read over and edit very slowly, and go through things a ton of times. Even so, I'd prefer she didn't change things that way, because it causes about twice as much work for me. A hard copy is more easily lost, but hard copies have worked out best for me. I think it will depend more on who your betas are than anything else.
