Both models have plastic handles which makes them very light and cost effective - less than 125 grams.
The Felco 300 (or F300) is a lightweight snip for general trimming and picking; especially good for dead heading. It's lightweight and features a bypass cutting style.
The Felco 310 (or F310) is also a light weight snip designed for picking and trimming but it has a very slim head for getting into narrow places; great for stems of flowers and fruit too.