Air Force

This seems to be about cyber transport - http://commguys.net/viewtopic.php?f=6&t=12943
And this one seems to be about client systems -
http://commguys.net/viewtopic.php?f=42&t=36872&p=250198&hilit=client+systems#p250198

Of course it's tough to tell from just one topic on each, but the first guy looks more disgruntled than the second. Of course your mileage will vary, plus people tend to post more about such things if they are disgruntled.

According to Indeed.com, the average salary in Cyber Transport System is $98k. No idea how big their population/sample size is -
http://www.indeed.com/salary/q-Cyber-Transport-System-l-United-States.html

And this is for Client Systems (average of $63k) -
http://www.indeed.com/salary?q1=Client+Transport+System&l1=United+States

Certainly the better your clearance level is, the more $$ you can command in general. Indeed also says top secret clearance average is $91k ( http://www.indeed.com/salary?q1=top+secret+clearance&l1=United+States ) whereas secret clearance averages at $87k ( http://www.indeed.com/salary?q1=secret+clearance&l1=United+States ) so the difference, at least according to them, is not a huge one. If it's a lot of work to get the higher clearance, to my mind, it might not be worth it.

Disclaimer - I work in neither field, and never heard of them until seeing your post. But look on Indeed.com and Salary.com for salary information. Keep in mind, of course, that things change depending upon where you try to work. E. g. salaries in Boston where I live tend to be higher but the cost of living is also a lot higher here than, say, in Kansas City, so while I might sock away more I also don't keep as much due to a higher mortgage. But also recognize, of course, that nationally-priced items (think automobiles) are the same in both cities and, in those situations, a higher salary is without a doubt better.