Best Tool for Bolt Cutoff

So I am trying to get my proportioning valve off, and at this point I have to cutoff the bolts attached to. But that is a pretty tight space I am not really too sure on what to use to cut it off. I thought about using a dremel but it just doesn't seem like the right angle. Or I could get a grinder and use a cut off wheel on it. Then I thought about using a sawzall but just doesn't seem like the best option. Finally I saw the dewalt multi oscillating tool.



Suggestions would be great as I have to buy one of these and would like the one that leaves me the most options. Once again that is a pretty tight space.



Thanks

Lee