From Agilent's Side-by-Side Comparison of Agilent and Tektronix Probing Measurements on High-Speed Signals referenced by me earlier:
Regardless of whether you use Tektronix’ or Agilent’s measurement performance standards for characterizing the performance of high-bandwidth active probes, Agilent’s probes outperform Tektronix probes on all counts as documented in this application note. Agilent’s 1134A InfiniiMax active probes using various probe heads (browser, solder-in) demonstrate less probe loading and more accurate reproduction of the signal applied to the probe tips. Even if you apply a Tektronix standard where you ignore probe loading and compare measured signals to unloaded/unprobed signals, Agilent’s probes still out-perform Tektronix probes when you compare the same probing configurations (Tektronix browser connection versus Agilent browser connection, Tektronix solder-in connection versus Agilent solder-in connection) and when you use identical sampling techniques (real-time), as shown in this application note.
With the introduction of the new 1130 Series InfiniiMax differential active probes,
Agilent adopted a new probe architecture/topology where the probe amplifier is physically
displaced from the probe head using precision RF transmission line technology for high-impedance connections. This new probe technology enhances usability and measurement performance for high-bandwidth applications. In fact, Agilent’s new 1130 Series
InfiniiMax active probing system was recently selected as the 2002 Test & Measurement
Product-of-The-Year award sponsored by EDN magazine. To our knowledge, this is the
first time EDN has selected an “accessory” for this award in the Test & Measurement category.
If it's not about marketing. What is it about?
IMO, I made a mistake in my first answer having suspected only Tektronix in marketing rubbish. It was be necessary to suspect both of them, remembering however that Agi was the defensing side. (And we need to recognize that Agi won this PR boxing round.)
I think neither Tek nor Agi but the engineer selects the method to measure and the corresponding background to interpret the result. Both Tek and Agi give the instruments for both approaches.
From the both documents I understand the one technical thing: they both beaten capacitance issues so well, they both beaten attenuation issues so well, but they beaten inductance issues not so, one did it better than another. I also assume that one patented some on this earlier and wider than another. It's very probable the philosophy (as PR base) itself and its difference (as PR task) were grown up on that.
As my conclusion, what do you prefer to buy from Tek, Agi, LeCroy, etc: a good thing you need or a puffing story about why other sucks? Tek/Agi drops its shit to the fan directed to the competitor, calling this "philosophy". Let's they taste their shit self, without us.
P.S. Both documents look like a WWF wrestling battle there each word and action are set up long before the battle begins :-]