Good morning and welcome to the group !
There is a currently active thread that will answer a lot of your questions as it started with essentially the same question:
Given your two choices, the SV650 would be a better choice for a first bike, especially if you can get a good deal on a used bike. Not too big, not too small. There are also a lot of DL-650 "Wee Strom" bikes available on the used market that would be a good choice.
You did not mention how far or what kind of roads you will be commuting on. The SV or DL will handle about anything, so again a good choice.
The Cliff Notes version of the thread above is this: The RT is a superb bike that many of us ride and absolutely love. While it is possible to jump on one as a first bike, it is probably not a really good idea due to the learning curve you will have in your first six to twelve months on the road. You are going to be heavily task loaded just doing the basics, and there is a good possibility you will, at some point, drop whatever you are riding. Fixing RT stuff is expensive !
As I pointed out to the other thread poster, you are purchasing your first bike. It will not be your last bike. Most people run through several over time and end up with something that really grabs them, which is what the RT will do after you have the skill set to appreciate what it does.
Gear: With some luggage, you can put your coat or whatever in them and use standard gear, mesh jacket, and overpants, to ride in. I am an attorney and run to the courthouse all the time, although if actually making court appearances, I generally use my car instead, simply because I am usually carrying a stack of files. Your biggest consideration is the weather. When it is hot, you will sweat. Cotton anything your are wearing will stay soggy all day. If it is raining, a good set of rain gear will do wonders, but you are going to get wet a bit in really heavy rain. Weather is where the RT really shines. Run the windscreen up and hide behind it, and you will be relatively dry as long as you are moving. Stop lights, well... you get a bit damp. Plan B: Pack the work shirt, pants and dress shoes in the case and change when you get to work. Many riders I know do that, and it works well for them.
As far as security, if you are on any bike, any size and somebody really wants is, they will get it, locks, security or whatever. Mostly nobody steals BMW, so parking next to Harleys (bait!) helps alot
At work, it is probably not a problem at all unless you are in a really bad area. Traveling, a lot of folks carry a big chain, a bike cover, and let it go at that. LoJack is a good option if you are really worried about it.
Good luck on the choice, and ride safe out there: Always remember that you are invisible and everyone is out to kill you and act accordingly.