Saniflo Greywater Pumps?

Working on the design of our kitchen remodel. Currently, the kitchen sink is on an inside wall, 2 feet from the stack. We're looking at moving the sink and adding a dishwasher, but putting them on an outside wall, 12 feet away. Our house was built over a dirt "crawlspace" but the dirt is only about 12" below the joists. I'd rather not run the DWV lines under the house, worry about freezing there, and deal with cutting into the stack at grade level, etc.

Is there any big downside to using a Saniflo Greywater pump system for the kitchen sink and dishwasher only? (Assuming it's properly vented) I'm thinking I could use this, and run the drain line through the ceiling instead over to the stack.

And how do I choose between the Saniswift model and the Sanivite?

Gravity always trumps pumps when possible, so I'd not consider using a pump when gravity would work. Other than the trap (which on a kitchen sink would be inside the house), a drain line does not hold water. Running water down the drain is not likely to freeze and plug up the line unless you have a slow leak that continually drips water down the drain line. So, I'd bite the bullet and run new drain lines to the new locations.

If you're going to the expense of remodelling your kitchen, avoid the grey water pumps. The saniswift and sanivite are fine for hand sinks, showers and short-term temporary usage but as soon as you start draining water that can/will contain grease, food particles or is 1-degree hotter than the maximum threshold, you will have issues. Most of this would not be covered under the extremely limited 2 year warranty - the company will make sure to tell you this repeatedly. Save yourself the grief and spend the extra money on installing proper drain and vent lines.

Using a pump to discharge water from a kitchen sink and dishwasher is almost guaranteed to create "eternal" problems. Call a plumber and let him deal with providing a proper drain.

I'll chime in just to say I agree fully with all the other posters so far.
Looks like really good advice to me.
Don't pump!