The 14'3" 7/8 Solstice and 14'4" 8/9/10 Steelhead Specialist are both fine steelhead and salmon weight rods. I wish I could compare them with the particular Scott rod you mentioned but I don't have enough experience with them other than having cast them at Denver and at claves where I thought they were fine rods. I can provide some input on the CND rods though...
The Solstice 7/8 provides a lightweight yet gutsy, versatile greasedline rod (that was it's orginal name). It's a great summer rod (7/8 midspey, delta, SA short, 7/8/9 windcutter, etc) as well as lighter grain winter rod (7/8/9 lines with tips). It flexes nicely but has a lot of punch with a high modulus IM8 graphite material. This is the first rod where I found consistency throwing a whole fly line in such light grain weight but the 15'2" 7/8 is even easier for that task. It's as a true to rating 7/8wt rod. During field testing fish to almost 20# were landed, but this is a rod that is light enough to give you the most out of every 6-8# summer run that torpedoes your muddler.
The Steelheader is an 8/9/10wt and I like lines in the 8/9 or 9/10 ratings (depending on the line). I like the midspey 8/9, the delta 8/9, the Carron 9/10 or 10/11, the SA 8/9 short, or other lines in that rating on the SH but the opinions vary on this rod because it's pretty accomodating in terms of line. It has enough power to take extended belly lines like the Grandspey and XLT, either 8/9 wt for shorter work or the 7/8wt for full head / overhand casting.
Although both are good summer and winter rods, if one has to choose consider your angling needs / wants. I would opt for the Solstice if you fish mostly summer and fall, and your winter fishing is effective with 7/8wt systems with tips. Maybe you want a rod that is not too stout because most fish you encounter are in the 6-12# class. Lighter line means finer presentation during low summer flows as well. But I might opt for the Steelheader if you fish larger rivers in summer and in winter go for bigger tips and flies in 8/9 midlength or 9/10/11 weights (short heads). The rod is gutsy enough to handle the upper echalon of steelhead and salmon that swim while still very pleasant to cast all day.
I hope someone fills you in on the Scott so you can get the full picture. We are lucky there are so many good choices out there.
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