In reply to pbphil169:
I've owned and used XGK's (pre-shaker and shaker verions) for fifteen years or so, and an omini fuel for the past two or three. However I can't directly compare them as I ran the MSR's on unleaded petrol, and the omnifuel on a clean stove fuel. Thoughts are:
1) If going overseas particularly N.America and many greater ranges, I'd go for the MSR. Spares more accessible and if in base camp or on trial should the stove break, other parties will probably have MSR's and spares to help fix. Also the scouring wire for cleaning 'feels' more reliable than the filter insert method of the Primus for dealing with dirty fuel.
2) Downside to the MSR is the fuel pumps break, having said that it took ten years to encounter this myself, but saw several others suffer this.
3) MSR's always need fiddling with, especially compared to the primus (though this may be in part a function of the fuel).
4) Primus looks and feels to be of higher quality and better manufacture, with more thought being put into the design, especially on little details
5) Primus simmers and can use gas.
6) primus needs longer to prime (i.e. more fuel squirted through at the start) than the MSR as its fuel line doesn't pass over the flame. Also because of this if its not fully primed at the start, it won't gradually 'settle' down. In my experience those from an MSR background always flare the primus on first lighting.
Overall I think the primus is the higher/better quality stove. But they are both good, and quality isn't the only factor to consider.