Well, to me, it would seem to depend on whether it's your first e-kit. By that, I mean, if you have an existing kit that you can steal pads from, it may not make as much of a difference, and may be well worth getting the Strike alone.
For me, I was used to having four toms and four cymbals (not counting the hi-hat or ride). Plus, I wanted a full kit to leave at my band's practice space AND one to keep at home. So it was more logical for me to go with the Strike Pro. Now, I can transport the module between my DM10 at the practice area and my Strike at home. I also will pack the Strike up from home to take to gigs. But this also lets me do any tweaking between practices, as we typically only have one of those per week.
I also have a preference that the main parts of my kit match, so I didn't want to just add one of my DM10 pads to the Strike. That may also not really play a part in your decision. I just tend to be a little OCD when it comes to stuff like that.
There is a functionality issue that I ran into, however. Depending on the cymbal you are transporting over, you may experience some issues. If it's an Alesis crash, I think it would work just fine. I have a couple of Roland crashes that would not trigger on my Strike module. The strange thing is that I have a Roland hi-hat that I use as a splash. No problem with that one at all. The Alesis hi-hat from my DM10 kit works as a hi-hat, but not as a crash. There may be ways around these issues, as I was rushing through setup at practice last week and didn't have time to do a bunch of testing. But the issue is there, just thought you might want to be aware of that beforehand.
I hope this helps shed some light and helps your decision!
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Shawn