For the past several releases Oracle has provided paired offerings for JRE 8, the latest being JRE 8u73 and JRE 8u74.
I cannot find any significant difference between the two and have been installing the higher numbered version. (There is also no recommendation that one should install both, one after the other.)
I have no idea if there is a functional difference; certainly nothing seems to jump out at me.
Anybody got a notion?

Oracle is not particularly forthcoming about changes in Java, but there is an ongoing effort on their part to continually strengthen Java and prevent its use in malware exploits. The battle against malware is a running battle and there is unlikely to ever be a "final solution", I choose to take every upgrade offered whether it is in OS X, Java, or an app. I have no intention of leaving the bad guys an opening that is easily preventable.

By-the-way I just notices that Java 8 update 73 Build 02 is a Critical Java Security Update

But that doesn't answer the question as what the possible difference is between 8u73b02 and 8u74b02. To me they seem identical, and even Oracle refers to them in a 'single breath' as 8u73/74.
8u74 would also include the Critical Java Security Update.

The Java Control panel still reports Java 8 Update 73 as the current version. Without performing a binary comparison of the two builds I doubt anyone could tell for sure if there was a difference and possibly not even then. On the other hand several years ago changing a single parameter in a single line of code in a million plus lines of code program brought down the entire telephone communications network for the eastern third of the United States. Similarly a constant used in the control program for a high frequency radiation machine used in cancer treatment allowed it to produce enough radiation to permanently burn and injure patients in a single burst.

In other words what may seem an insignificant change in an application can have a huge impact on the results produced by that program. I have seen a new version of a program released because of a typo in the internal documentation in the source code that had no impact on the program's operation, but it could have created an opportunity for error in a future release by misleading a developer making a change.

The only place I see Java show up is under Plug-ins in my browser (Firefox): Java Applet Plug-in Java 8 Update 74 build 02. No clue what else is on my Mac; Spotlight doesn't show anything. I see no way to access a Java control panel or anything else in the application. So I'm still in the dark.

Oracle's Java installer places a pane in System Preferences. Clicking on that pane launches another window outside of System Preferences that has among other things…

• A "General" tab with settings for network options and temporary file settings
• An update tab that lets the user know if they have the currently recommended version of Java
• A Java tab to manage various JRE environemnts at either the system or user level
• A security tab where you can set the level of protection at high or very hiigh, specify sites that can run Java applications that do not meet the security requirements, and a place to manage the Java security certificates
• An avanced tab to control debugging tools, the Java Console shortcuts, installations, etc.

If the Java Pane does not appear in System Preferences your installation is incomplete, go to java.com download and run the installer.

By-the-way, as of 15:30 February 7, 2016 the Oracle/Java web site identifies Java Version 8 update 73 as the recommended version for OS X. I didn't see any mention of update 74?

Found the pane in System Prefs but have no idea what I might do with it. I only thing I care about is that when I update the application it updates the Java Applet Plug-in in Firefox.
EDIT: A half hour later I opened up the Java pane and meandered through the settings. When I checked for updates, it advised that I have "the currently recommended version — JRE 8 update 74". So I guess that answers the questions all around. Rah.
And thanks, artie, for the additional input (below).

As for the latter, whenever I go to Oracle's JRE page there are always 2 updates stacked on top of one another, most recently JRE 8u73 on top of JRE 8u74, with no info as to which I should choose (so I take the higher number of the two).

Took a look to see what's up...