Fragile: The most obvious drawback. Glass can break if dropped.
Heavier: Glass is heavier than plastic, making it less ideal for very large bottles or for travel (though small travel sizes are still common).
More Expensive: Typically costs more than comparable plastic bottles.
Glass Color: Choose Amber or Cobalt Blue for anything light-sensitive (oils, toners, tinctures). Use Clear Glass for short-term or non-sensitive products.
Sprayer Quality: A cheap sprayer will ruin the experience. Look for ones that promise a "fine mist" if that's what you need. The pump should feel smooth and not leak.
Seal: Ensure the sprayer head seals well with the glass bottle to prevent leaking and evaporation.
Capacity: Common sizes are 1oz (30ml), 2oz (60ml), 4oz (120ml), and 8oz (240ml). Choose based on your usage.
Material of Sprayer Parts: Even with a glass bottle, the sprayer mechanism itself will have plastic and metal parts. Ensure they are compatible with your liquid (e.g., some essential oil users prefer all-plastic internals to avoid corrosion).

