Compare in terms of what?
In general, though, while I find the Inova lights to be good quality lights they pale in comparison to the LED Surefires that I have (I have an E2e with KL4 and KL1 heads (both old and new styles), an L1 (old and new optics) and a U2).
Fit and finish wise, I find that the threading on the Inova to be inferior to the Surefires. More than once it felt like I was in danger of cross-threading the tailcap as I was putting it back on to an Inova light. It never feels that way when I am using a Surefire light. I will say, though, that the Inova looks more elegant and stylish to my eyes whereas the Surefire designs look relatively utilitarian. However, this is purely my own opinion.
Output wise, the X03 definitely puts out more light than the L1s and the KL1 heads. To my own eyes, it can hold its own against the output of the KL4 head or the U2 on high. However, it does have the 'ringy' beam due to the TIROS optic. The KL4, the old KL1, the old L1 and U2 all produce a smoother looking beam. The new KL1 and the new L1 with the TIR optics also produce a 'ringy' beam but in my opinion it is not as pronounced as the beam from the X03.
In terms of size, the X03 is noticeably larger than the E-series lights (E2L or L4) and the L1. Compared to the U2, the X03 is slightly longer but the U2 has a larger bezel.
Price wise, well, Inova lights are definitely more affordable than Surefire lights. I think the most affordable LED light that is in the Surefire line is the E1L and that retails for almost $100.00. The Inova X03 retails for much less than that.
If you want more empirical data, there is always
FlashlightReviews.com.
If you want photos comparing the sizes of the Surefires to the X03 let me know and I can take some and post them.