I travel with a drumset, bongos and a cajon quite often, I have also moved between countries. So I've had my share of both drum bags and drum cases. There are pros and cons to both:
- Bags are lighter, cheaper and if thickly padded offer a better protection from large area impacts (such as being dropped), but offer virtually no protection from impact by hard or pointed objects such as a door frame, a cymbal arm, etc.
- Cases are heavy and expensive, offer excellent protection from hard or pointed objects, but often not good protection from overall impact, such as dropping, due to little or none soft, absorbent materials inside.
The Gewa SPS line of bags are a unique and brilliant concept: they simply combine the best of both worlds. They are light and relatively inexpensive, they have plenty of padding to protect from overall shocks, yet they feature fiberglass plates that give them the necessary stiffness to protect from impacts by hard/sharp objects.
Honestly, I don't think there's anything better out there.
PROS: light, cheaper than hard cases, offer great protection both from overall impact and hard/pointed objects impact.
CONS: they could use some additional pockets for accessories.
If you value your instrument, get these, period.