Deanna,
I'd question having two trailers, simply because if you have one, short, punchy one that works - what's the sense in having a second? I can see where you're coming from - and why having a longer one on your site might give potential readers more information - but then if you've got them to your site already, then your first trailer has done it's job (or half its job - its real job is to generate a sale!)
With regards to format - it's hard to say what works best. I don't know whether a dramatization is any better than a pictorial slide show or vice versa. There are certainly excellent (and awful) examples of both. I think the bottom line is whatever route you take, make it look as professional as you can. By that I mean make it look as good as you can/afford. Take the time to invest some money in your trailer - download some high quality royalty free images from somewhere like istockphoto.com instead of ripping them off the internet. Think also about purchasing some royalty free music and getting some professional voice over (again, if you can afford it). The result will be well worth the cost.
The biggest problem with book trailers is that authors, by definition, aren't that au fait with editing programs -and so typically, you end up with trailers filled with all these fancy transitions (a change from picture to picture) because people think they look cool (the page wipe is a favorite - well, because it's a book trailer of course). Honestly, don't do it. It looks cheap and cheesy. The best thing you can do is a jump cut. Just cut from one thing to the next. Next time you watch a movie or show on TV, see how many transitions you see - if you see any, you'll probably only see a dissolve (a fade from one picture to another) - but other than that, I'll bet you can count them on one hand.
There's another reason for not using lots of transitions - it freaks your compression software out. Go find a book trailer and watch the picture when the images flip around or over - you'll see lots of digital break up/pixellation. That's because the compression used to get the file small enough to upload can't handle huge amounts of movement in the picture. Better just to use a straight cut.
Other things I wouldn't do...don't take small pictures and blow them up to fit the screen. Pictures are based on pixels. When you enlarge them, you shoot the resolution all to hell and they look awful, having the net result that your trailer will then look cheap and nasty again. Again, use large, high quality source images if you can.
Also, don't stretch your trailer out to match a piece of music. Either edit the music or fade it out. Don't fill. Like I said, after a minute, I'm getting bored.
Play around with your compression software. Change the settings and make sure you are getting the best looking file you can create.
Finally, ask around. Is there anyone in your family or circle of friends who plays around with a camcorder? If so, they probably dabble in video editing and Photoshop - and they can probably put together a much better video than you can - better still, they might even do it for free.
Hope that's been helpful. Sorry, I didn't mean for it to turn in to a lecture.