No, all 5kW machines are not created equally.  5kW is simply the amount 
of power that is required to run the lamp and does not necessarily relate 
directly to the light output.

A few things to consider:
- Different lamp types (i.e.: capillary, straight mercury vapor, 
iron-doped) emit different light spectra and intensities.
- Jacketed (water-cooled) lamps add an extra layer of glass and a layer 
of water for the light to go through, so you can lose quite a bit of 
light there.
- Yes, you should focus on exposure plane intensity (but make sure that 
the intensities were measured using the same radiometer, because no two 
measure exactly alike.)  I've got some field test data comparing the 
machines you're looking at, if you'd like to get in touch with me.
- As you probably know, you'll get better resolution and straighter side 
walls if you hit your resist with higher intensity for a shorter time.  
(Not to mention the production rate increase from a short exposure 
cycle.)
- What Scott Kivi mentions about cooling is important, too.  Look for 
high a/c BTUs and a well-controlled air flow over the exposure plane.

Send me e-mail if you want to discuss anything else.

- Scott Thompson

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