D'Addario Helicore strings provide the warmth and depth you would expect from a synthetic core while having the strength and stability of their (actual) metal core.
Extremely fast break-in - within hours they are stable and holding their tuning perfectly.
Nice clean, bright sound.
If you like experimenting with different tunings, they are strong enough to cope with being tuned up and down frequently and will handle a little extra tension than the standard pitches.
The wound 'E' string plays significantly better than the plain steel version - worth the small extra cost.
A great all round, well behaved string . If, like me, you play a mixture of styles - classical, folk etc and want to use the same violin for everything, these are pretty good for any style of music.
There are some other brands that don't wear out as fast, but since those strings cost twice as much (and remember Helicore's instant break-in) there's no advantage really. I do experiment frequently with different strings but always return to Helicore as my firm favourite.