My preferred method is to force carbonate water in the keg and bottle on top of syrups in glass bottles using a BMBF
. That keeps the kegs clean (no strong flavors in keg), they carb faster and more fully (due to absence of sugar in keg).
If you can keep your keg chilled when you bottle, and keep sloshing to a minimum, you can keep a fair amount of co2 in solution and have a nice carbonated beverage. With careful sanitation, I've even kept unrefrigerated bottles stored for a number of weeks without loss of carbonation, overcarbonation, or change in flavor. The only things that have rendered my urefrigerated bottles undrinkable so far is that some with excess solids such as spices or fruit pulp will settle out and create a sludge on the bottom over time, or if I cut corners on sanitation, then they start to tast a little yeasty after a while.