I bought the Hitachi 10" slider for my business. I'm a handyman, and I end up doing a lot of trimwork on houses. (Rehanging doors, replacing rotted exterior trim, remodels, etc.)
Straight out of the box, the Hitachi slider is by far the most accurate piece of machinery I've ever owned. I've talked to a number of trim carpenters who agree. And the majority of sliders that I see on construction job sites are Hitachi 10" (I think that the model is the C10FSB, but the newer version has a laser, and is a different model)
Without any adjustments, I took my new saw to a customer's house, and did three rooms of trim, including crown and chair rail. The saw did a perfect job.
If you think of the motions that you'll be making while you're using a sliding miter saw, you'll realize that 'sideways' is sort of naturally precluded. You're hand will be making a sweeping (down and away) motion, with the sliders guiding it. Believe me, I've made that motion a million times.
Get the Hitachi. Be proud that you have the same tool that the true pros use. And get those accurate cuts that many only dream about.