I, like many hammered-dulcimer players I've met, have a bag full of hammers. However, I find that I only ever use one pair, a set of double-headed hammers (padded on one side, unpadded on the other). Is this typical, or am I missing out on some important aspect of playing by not varying my hammers? If I should be using more than the one set, what are the characteristics that matter most? Weight? Width of the striking surface? Something else?
The ability to phrase your playing into an almost vocal-singing-like quality versus the ability to energize your playing into highlighting the percussive nature of your instrument, to me, is indeed an 'important aspect of playing' hammered-dulcimer. Long-flexible-light-soft-bouncy hammers affords vocal quality more readily, and short-stiff-heavy-hard-unpadded hammers brings out percussive quality more easily. the 'bag full of hammers' are useful for uncountably more subtle choices like long-and-stiff, heavy-but-really-padded, etc. Of course, choosing which hammers to use depends on the feel of the song.
Examples of vocal-like playing:
Examples of energy-percussive playing: