I think for 1-2 books, I would be indifferent though I might prefer 1DS because they offer much more options for fine tuning (ipad, sony reader, iphone, nook, etc.). However 1DS would probably cost a bit more (though it looks like fine tuning is now offered for free to non-platinum members). Also, 1DS for non-platinum members will probably take a long while (probably 30 days+) and OCR + book title are extra cost options ($1/set each (set=100 pages)).
For bookscan.us, I think you would pay $4 for each BE (300 pages) and it would include book-title + book-cover-picture + OCR + epub or mobi file (option E at http://bookscan.us/order-page.html
). Probably the Mobi/PRC option is best since you can side load it to the Kindle and also upload it to your iPhone for use with the Kindle app on there. So unless you are really short on storage space I would probably go with Bookscan for the low cost and fast turn-around. But if you need to really get the filesize down and can pay a little bit more, 1DS might be the answer. Hope this helps a little bit.