Hi Dustin
First time I'm posting but I'm kind of a camera guru. Background: I'm a NPS (Nikon Pro services) member, Was a CPP (Certified Pro Photog) - PPA, Adobe Certified Expert - Photoshop CC, I assist in teaching at 2 colleges.
First of all, in my biased opinion, there is absolutely no reason to switch brands, especially if you already own descent lenses. I have to be honest with you, the 18-55 is pretty much garbage, but the 70-300 and the 60 Macro are pretty good lenses (especially the 60 macro, you have a nice, sharp, and fast lens there.) So you have 2 lenses you can work with. Switching from your Nikon D3200 to a Canon 5D mark 2, If I'm correct (Don't know too much about Canon), but I think you're going from a cropped sensor to another cropped sensor. In matter of fact, the sensor size on a Canon is actually a bit smaller than the Nikon (Bigger is usually better in most cases). To get technical, the Nikon has a 1.5x crop factor whereas the Canon has a 1.6x crop factor. If you don't know what this means, don't worry about it, but all you have to know is that the Nikon has a slightly larger sensor.
BTW, the 60mm lens, whether it's a "DX or FX" lens, doesn't matter when you put it on a DX or cropped sensor body. The 60mm lens will have the "field of view" of a 90mm lens, but it will NOT change the characteristics of the lens and become a 90mm lens. Hope this makes sense. The advantage you get in a dedicated 90mm is that you will have more lens compression, more bokeh, etc. The reason why I mention this, is because I noticed that you said you want to do more macro work. What you'll get out of a longer lens (I would get a 105mm if I were you) is the lens compression, and the ability to be further back away from your subject so that more is in focus. Why? the closer you physically are to the subject, the more "out of focus" area you're gonna get. For example, if you are so close to someone's eye, maybe the pupil will be sharp but the eyelashes will fall out of focus,, stand further back and the eyelashes will start to come back into focus also. What a macro lens does is allow you (due to it's incredible "minimal focus distance") to get so close to the subject that you can get a 1:1 ratio in the frame. But the longer the focal length, the more you can get in focus, cause you are physically further away to get the same ratio in the frame as opposed to using a shorter lens. Makes sense?
Also, the 24-70 is a very versatile and much used lens by many photographers. It's got a great minimum focus distance and a mid range focal length that is useful.
Anyway, enough of my rambling, in my opinion, buy good glass and invest in an actual upgraded body (when you're ready for one). When I say upgraded body, I mean a full frame camera. While using Nikon, I would strongly suggest when investing in lenses, buy the FX or full frame lenses. They work in your DX body for now and will follow you when you upgrade to a full frame. The DX lenses works on a full frame camera, but it doesn't make any sense to put a DX lens on a full frame camera.
Hope this info helps
John
