Geeze, some people are too hung up on what they THINK others might be thinking of them. Bottom line is you ain't important enough for the public to notice your gig bag, let alone make moronic assumptions about your musical skills based on it. Most punters don't even know the difference between a bass and a guitar, how'd they know a good gig bag from a crap one? Methinks your ego is too inflated if you think folks are actually paying attention to stuff like this.
If you want to use a gig bag, get one that's solid, protects your instruments well, and will last (i.e. the straps won't come loose). Spend some time periodically examining the seams and attachments so you can catch problems BEFORE the thing falls off your back and down the stairs. And don't discount hard-shell cases. They're still the best way to get a bass or guitar to and from gigs without damage. I only use the gig bag if I'm carrying the instrument on the car seat next to me. If I gotta put it in with anything that might move around it's in the case. Things like the heavy gig bag I carry cords, tools, mics, etc. in; like the amp head in its bag, like a mic stand or two, and so on have a way of shifting around in the back of the van or in a car and I don't want my bass trashed because I was a lazy putz who didn't want to schlep the hard case around.
But get over yourself and your idea that people are actually paying attention to your bag. Put your time and energy into playing, not considering what others might think.
John