I'm going to answer the question you are more-or-less asking, I think: "How do I evaluate if this is good for my career/compensation/self."
It's hard to say how support compares to engineering in terms of compensation and even career potential at a specific company; a lot of that depends on what the company does. But it's not hard to say that development/engineering is a better long term move for your career as a whole. Even at identical compensation (today), support will have a lower ceiling than engineering; that's because support doesn't take as much creativity and intelligence (or, is seen not to - creativity and intelligence can benefit you very strongly in support, but that's another story.)
For you, though, the easiest thing to do is to look at what information you have about your company's career paths. Look at other not-new engineers, and other not-new support staff. How quickly did they move along their career paths (if you have defined ladder roles)? You probably can't find out their compensation, unless your company is more transparent than most, but you may be able to ask about compensation for the general ladder roles (ie "Support Tech II" etc.).
More important than salary for each role, though, is how easy it is to move up. Engineering typically gives you more of a chance to stand out than support; while both have some opportunity to stand out from the crowd, engineering has a higher ceiling in terms of making radical improvements or even new products - and a more obvious link to profits. As such, if you're really good, you have a good chance to move quickly up the ladder; in support, it would typically take you longer.
Support also - except at very mature companies that are no longer shipping new products - typically has a harder time getting additional resources (in terms of salary raises, for example).
More than likely, what they're thinking is moving you to engineering to let you show what you can do. It's a lateral move for now - perhaps no salary bump - but if you show you're good, you will move up and get bigger raises; so for your future, this is a good move.
All that aside, what you should do: talk to your immediate boss, or someone you trust at the company. Ask him/her what the prospects are for improvement. Maybe even see if they can get you a meeting with one of the folks who decided to move you - ask them why. Make sure to do it politely and without challenge: you just want to know why they picked you. Asked with appropriate humility, odds are you'll get an answer that is along the lines of:
We see great potential in you, and want to give you a better chance to grow. We can't pay you more right now, but if you succeed the rewards will come.
Of course, if you do succeed and the rewards don't come, don't be too surprised; it's business. Figure out how much experience you need at this position in order to apply for a better one elsewhere; 3-5 years is usually about right, but even 2 years is sometimes enough. Give them that long to show you they care; if they don't, move on quietly to a new position elsewhere at that point.