I'm looking for a spinning rod mainly for lightweight lures and plastics. The two I've been looking at are the Fenwick HMG spinning rods and the new St. Croix Mojo spinning rods as these two are in my price range. I've heard that the SCIII blanks in the newer mojos are a significant upgrade over the SCII they used to use but I'd like some opinions on the two. I'm primarily interested in sensitivity but other concerns are durability and use in saltwater. Thoughts?

IMHO, having owned both:

Fenwick HMG > SCII Mojo in the "bang for the buck" and performance department. No exp. with the latest Mojo, I don't even think they are available yet....but I have owned other SCIII rods (Rage and Avid), and am also of the opinion that the HMG offers more bang for the buck than those as well,with little to no decrease in performance despite the price difference.

Thanks for the feedback. I just noticed that the new model listed on the website is slated for 2016 so I guess I can scratch that off.

Both of those rods are extremely durable and may last you many many years. For the price there are certainly rods that are more sensitive, better balanced, and higher performing but will not outlast either of those rods. If you are getting into saltwater you may consider the HMG. I would say the Mojo is very bass fishing specific due to its power throughout the midsection of the blank. The HMGs are a little slower and offer you some forgiveness when dealing with pulling fish from deeper waters. 

The new model HMG is hard to beat at the price point, I have a bunch of Fenwick rods anymore, they offer me great performance at a value price point.  The Mojo with the SCII graphite isn't a bad rod but the HMG is going to be lighter with better sensitivity, I haven't got a look at the new one with the SCII graphite but if you are going to get the Mojo then wait for the new one, if you want it soon the HMG will fit the bill and I'll bet you will like it.