What do your customers want? Through years of trial and error I find that my customers ask for sterling silver. In particular when they see something they realy like, but have a skin allergy, it is sterling silver they like it to replaced with. Never had I anyone ask for an artist made, bead-stitched clasp to be replaced. With these we have to make sure that they stand the test of time: nice and firm, with stitches reinforced, maybe even a toothpick worked into a toggle to stiffen it up. Aluminium toggles are nice and light, but can be so soft that they lose shape when used carelessly (not sure if aluminium work-hardens). With soft sterling silver you can hammer it until it hardens; be careful you retain the shape.
Magnetic clasps are great, if used appropriately: note that they are most often metal, and may not be sterling silver. Be very careful using them on bracelets: they are easy to get caught and lost. I test-drive most of my jewellery, to be sure they stand up to use. Let me tell you that I have lost cherished bracelets with magnetic clasps. You can add a safety chain, but that can get caught too. In general I would recommend magnetic clasps only for necklaces, and then being large enough that fingers can grasp them easily, rather that the wearer having to tear it apart at the strands. I have once been told only ever to slide magnets apart, which sounds sensible to me. Pass it on, not many people seem to know.
One more thing: Often magnetic clasps are used with the ends of the beadwork glued into the clasp. When I spent some time in a tropical climate, let me tell you, I have not encountered any glue that stands up to the conditions of humidity and salty air. In short: You are the expert in for your customers.
I have seen beautifully custom-made, bead-covered magnetic clasps, carefully integrated into the beadwork. Taking my hat off to them.
It's my favourite - but you have to know what you are doing with it: Small toggles can be fiddly, and sometimes useless if you like to be self-sufficient in putting on your jewellery. When buying toggles I try to chose them over 15mm wide, sturdy, less frilly. They can add length to a bracelet, depending on how you place them (you can place them 10mm inwards from the very end, if that works with the style). Toggles can be great for necklaces; however, one of my friends lost a toggle necklace when her long hair got caught in the clasp.
These are great because they always fit the colour scheme of the beadwork. But they add at least an hour’s worth of work to your piece - make sure you know what you charge for. These toggles can be a statement in themselves, depending on the placement in the piece. Personal favourites are the open, double-sided triangle, or the open warped square that can be so well interacted into an arrow bracelet (to this one I like to add a dome button, to securely hold the flap down).
These can vary in size. I have used some larger parrot clasps for necklaces as well as bracelets, and they work well. They have to be large enough to be easily manipulated by the wearer, and still look decorative.
I have been disappointed with parrot clasps attached to bars, sometimes used for wider bracelets. They always seem to sit too close to the bar to be easily opened. They move to the top when wearing, so you show off the clasp and not the bracelet (still trying to make the clasps heavy with added pendants so the weight keeps it down; that goes for toggles as well).
Slides are great for wide bracelets. You can really make tidy finishes with slides, if attached with care and thought. Particularly when attached to a wide bracelet they still have to have a certain flexibility: imagine the entire length of the slide needs to be able to, well, slide into the other half, and that often on an exact angle.
You see, trial and error is the key. Creativity and experience will teach you what works best for you. Enjoy the ride!