I have the most experience with Helicore, Prim and Pirastro Chromcor steel strings.

I liked the tone of the Helicore mediums but had read on the Fiddle Hangout about problems with their wound with aluminum A string. I’ve never worn through the windings which seems to be the main complaint. But, I ran into several wound A’s that were “wonky” in their tuning. I tried the Helicore titanium wound A and had the same problem with one of them. With most of the A’s, you could get them in tune and they didn’t seem to hold well. I also replaced the Helicore E with a Goldbrokat E and Pirastro Gold label (and use them with the Prims and Chromcor’s I have on my two fiddles now) and thought they sounded better. The Helicore are steel stranded with windings (with the exception of the E.)

I gave up on the Helicore’s and tried Prims and Chromcor’s and have those strings on my two fiddles. They have a single steel core with windings (except for the E) The Prims are the lowest cost (around $26.00 at Southwest Strings) and the Chromcor’s are around $44.00. I much prefer either of these strings over the Helicore’s. I think the Prim’s are a bit brighter than the Chromcor’s and I tried both strings on both fiddles. One likes the Prim’s the best, the other, Chromcor’s. They hold tuning well and stand up to cross tuning very well.

A tip in case you don’t know. I always “lube” the nut and bridge grooves with graphite from a pencil. This helps the string slide when adjusting/changing tuning.