It will depend on a few things but here is a quick opinion I have about the 2.
Cost typically around 1350 or so
Now they are readily available
Have been very consistant and on some fast cars
OEM builder- Lack of warranty
No real tech support- Lack of warranty or assistance if there is problems.
Moran Power Tip 5's
Custom injector built for racing applications.
Excellent tech support
Can be upgraded. They can be spec'd from 200-600 lb/hr. If switching from 235 to 275 simply pay the difference in price.
Cost- They are $1504 for a set of 235's. Not really a bad thing cosidering it is a billet item, but they do cost more than the Siemens
Large in size by comparision. They do fit in typical mounting locations, but if they need to be side by side you will have to verify clearance.
I am a dealer for both and both are good products. I have had Moran make me custom injectors and they have proven better than anything else we have tested, per application. They stand behind the product and constantly work to making the product better.
Siemens are the largest OE injector that I am aware of.
If you have any specific questions just ask away, I am sure someone can help.