I'm really not in to screeching rock, but more middle of the road pop. Which Orange Tree Sample electric guitar library would suit me best? Texas Twang or Stratosphere or something else? I need to decide before the end of the Orange Tree Samples Group Buy.

Either of those two, or Strawberry would meet your needs, but I can't say which YOU would prefer.
 
All the guitars are sampled clean, (from the pickups) so you can either use the built in FX /amp sim presets or roll your own. There are great sounds straight out of the box, or you can turn off the Kontakt effects all together are rout through another amp sim like Amplitube, TH3 or Guitar Rig so they are all capable of a huge range of tone.

fishmusic
I'm really not in to screeching rock, but more middle of the road pop. Which Orange Tree Sample electric guitar library would suit me best? Texas Twang or Stratosphere or something else? I need to decide before the end of the Orange Tree Samples Group Buy.

Strawberry is the one I usually reach for first. I, too, tend to hold my screeching down to a minimum. But Strawberry can do that, too - if you want it to. 
 
However, if I could only have just one OTS electric guitar, one that I'd be able to use in nearly any project, it would be the Rick 12.
 
 

I'd vote for dracus, it's very well rounded and versatile. Strawberry is fine as well. 

Many thanks , guys. Great food for thought.
Is there any merit in buying a more recently issued library BECAUSE it is newer? In other words, are the earlier ones on a par with the newer ones in their functionality, quality, etc?

to be honest, I have strawberry and dracus, and strawberry (older) gets much less use. You might youtube some reviews so you can hear them in action.

fishmusic
Many thanks , guys. Great food for thought.
Is there any merit in buying a more recently issued library BECAUSE it is newer? In other words, are the earlier ones on a par with the newer ones in their functionality, quality, etc?

Good question. The answer is that OTS has routinely updated older products to add new features. Last year every library got the latest scripting engine, including the oldest one in the collection. This way, every guitar has essentially the same user interface and basic capabilities.
 
There are small differences between instruments, but they're intentional and reflect each guitar's personality. The oldest library (Strawberry), for example, has a pinch harmonic articulation that the newest library (Texas Twang) does not have.

I actually really like the tone of Strawberry, so I use it still*
 
 
(*And I, sadly or amazingly, have all but 2 of the guitar libraries.....which I will purchase in this group buy to complete the collection.)

I'm using Orange Tree for a lot instruments except the guitars. ( I'm a guitarist.) I'm using their Upright Bass, Evolution Grand ( which is a pretty great Piano ), Vibes , Marimba, all great stuff. I have the Harp coming on this coming group buy. - thinking about the flute samples too.

SmokeyJ628
I actually really like the tone of Strawberry, so I use it still*
 
 
(*And I, sadly or amazingly, have all but 2 of the guitar libraries.....which I will purchase in this group buy to complete the collection.)

 . . . dang you, now I have to go investigate Strawberry . . . and the OTS demos usually put the hook right into my mouth. I have 5 of the OTS Guitar libraries, just not this one, yet.