I feel like they're always over selling how attractive Bo is.
Anna Silk is nice, no obvious deformities, but in-show everyone acts like she's Angelina dressed up as a smuttier version of Tombraider... I'm not that into Angelina either. Too plastic in the face area. I suppose if 90 percent of your fanbase is already having sex with realistically contouring dolls, it's only following market trends to appear indistinguishable form a life sized opposable action figure with semiworking genitals and bonus lodging areas.
But Bo is probably unwittingly pumping the room with military grade pheromones that has everyone overreact to her presence that she could look like Jane Lynch (Not that there's anything wrong with that.) yet still be treated like Marilyn Monroe in her heyday.
I recently started re-watching the series from the beginning. (I just finished "Something Wicked This Fae Comes" last night.) When I got to "Vexed," which was the first episode they ever shot, I noticed that Bo looked & felt a lot different in that episode than she usually does. In many of the scenes, her make-up seems more subdued, there are noticeable lines beneath her eyes, her skin tone (and, indeed, the show's entire color palette) seems more desaturated, and her personality is much more cold & bitchy. Overall, I find her far less attractive in that episode than I usually do. For that matter, when I see the actress in interviews, I find her considerably less attractive than the character. Anna Silk clearly already has some strong genetic advantages. (It's like she took all the best bits from Kate Beckinsale & Jennifer Garner and smushed them together.

) But, ultimately, I think it's a combination of acting, lighting, and make-up that give Bo that final WOW factor that pushes her into the stratosphere.
As for Lauren, I think Zoie Palmer has an underlying cuteness. She deserves her props for that. I just have such a hard time getting into the character. She's just lacking in personality compared to Bo & Kenzi & Hale & Trick. And when they did start making "super science geek" her actual personality rather than just her job in Season 2, it felt like a nice effort but too little too late. (Although, when she does go into super-geek mode, she reminds me of Lilith from
Frasier. Coming from me, that's a definite compliment.)