Updated: Oct 25, 2019
Guitar strings are sometimes a confusing topic, you know what gauge you like (String thickness') but then bombarded with an array of different strings varying in material, price and the question of coated or not coated strings?
Where to start? - Start with standard, un-coated guitar strings.
D'addario's XL range of strings are very popular. Reliable, stable and feel like a standard set of guitar strings. They have a Hexagonal shaped high carbon steel core, wound with nickel plated steel. This translates to a guitar string which is strong and bright in sound. Reasonably priced in Music Shops from £6.49 - £7.50 it's a stable set of strings that isn't too expensive.
D'addario's NYXL range is a development of the XL range. The carbon steel core is also break resistant and this is wrapped in a more advanced nickel winding, which reacts much better with the pickups giving an increased mid range, 'more bite'. The plain strings have a "fusion twist" making them stronger and much more stable. They are more than the XL's starting around £12.99, but the string's brightness does not degrade as quickly as the XL.
Having played the NYXL's and compared them to the XL, the specs translate into a completely new string rather than an upgraded variation on the XL. They last longer (by 4x as much in my case), are much more stable when being used with a tremolo system and bend so much easier.
This is a method used for improving the life of a guitar string. Players sweat and dirt from hands gets into the string and breaks down the string, either to the point where it snaps or sounds dull. Each manufacturer has a different method of constructing and it has been met with mixed responses. By adding a coating to a string you are effectively dampening it, making it sound duller. So the string may last a lot longer but maybe, subjectively, just as dull as an old set of NYXL's for instance. These strings can also feel 'a bit like plastic' as one of my customers described so not as comfortable as a standard set to some players. The previous version D'addario did was called the EXP.
The D'addario XT Series:
This is what D'addario aimed to improve with the new XT Series. I will be honest, I have never been a fan of coated strings as of the reasons above.
The XT range features the same steel core and plain strings as the NYXL range of strings with has regular wrap wire on the wound strings. (nickel for electric guitar and phosphor bronze for acoustic). The core from the NYXL range gives it the brighter sound which you wouldn't usually get from coated strings. Which is a major reason why these are an improvement from the EXP range.
A thin hydrophobic (repels water) coating is applied to every string. Meaning sweat can't theoretically corrode the string, as you only need a thin layer most of the sonic resonance is maintained. Compared to the EXP, you gain so much sonic quality and compared to other brands it's also a big step forward.
If you directly compare these string to an NYXL, the string isn't as bright initially but sustains just the same. I have put the XT series on my Stratocaster, the strings sound is more worn in initially. But compared to other brands of coated string the XT series responds the best in my opinion. You get a string that is just a very slightly dampened NYXL, but for a much longer string life expectancy. Compared with the XL it is a vast improvement in terms of tonal clarity and feel.
Personally I like the new XT range. The slight dampening, long life and the feel of the string is great. If you find the NYXL's a little too bright, then the XT range is a great go to.
Feel is the largest factor in buying any string, and the 'plastic' feel I can report isn't inherently there. Compared to the NYXL and other standard strings, this set just feels smoother. It's a natural feel with all the same characteristics as the popular NYXL's but even smoother feel. Long periods of playing is where this is seen, much better on your fingertips so for those gigging or starting out and wanting to play for long periods these are silky in feel, sliding up the fretboard results in less friction which is think is great for acoustic players especially.
The XT's are the new leader in the coated string category, it is not a choice now of longer life but sacrificing sound and feel. But a string that feels like a guitar string should but so happens to last a bit longer.
If you want a very bright sounding string that last a long time, get the NYXL's. If you want a slightly warmer tone (but still brighter than standard XL's) then the XT's are perfect.
XL - Standard string, cheapest.
XT - Premium String, mid range price, longest life, long sustain, warm sounding.
NYXL - Premium String, mid range price, long sustain, brightest sound.