Best practices for using subcircuits and hierarchical blocks in LTspice
Hierarchical or subcircuits are the same, after LTspice flattens the netlist. You can see this by checking Generate Expanded Listing in the control panel, the Operation tab.

The advantage hierarchical schematics have is the direct graphical access through the symbol editing, where you can open its contents as if it were a schematic, and easily probe voltages, currents, powers (needs the two Save subcircuit ... options checked in Control Panel &gt; Save Defaults). You can also probe inside plain subcircuits, but you have to check the expanded listing in the error log; it's more cumbersome, but not impossible.

Overall, hierarchical designs are more user-friendly, but the disadvantage is the lack of encryption. Subcircuits can be encrypted to protect the contents, hierarchical designs cannot be. The expanded listing does not work with encrypted libraries, which is to be expected, therefore you are not able to save and plot internal quantities. Also, a subcircuit is more compact, typically one file, hierarchical schematics can be more than one. Oh, and you won't see nice yellow symbols...

Both ways, hierarchical and plain subcircuits, allow for external parameters to be passed on, such as your Vs={Vcc} example.

None is faster or slower than the other in terms of computations for same designs, since, as I mentioned before, LTspice flattens the whole schematic into a netlist, which is nothing more than a programming language for SPICE.

Which one to use? Take your pick. In general, if you're working on the design, choose hierarchical for easy, graphical access, so that the end result can be transformed into a subcircuit that's ready to be encrypted, if you so desire.




  As a subcircuit, I'd have access to the Components Attribute Editor and a few more fields for setting up parameters as opposed to the single PARAMS line that the hierarchical block uses


Those fields mean nothing in terms of netlist, and the names shown in the component attribute editor are also flattened: if you check the netlist, all the lines get cropped up into a single line that belongs to the subcircuit.

They are only meaningful as some combinations, in terms of the order in which they appear in that line, and which has differnent effects together with the symbol: in some cases, it's possible to prevent the symbol from being edited. See, for example, an opamp from the existing library and try R-Click, with or without Ctrl -- it will not let you. This goes hand-in-hand with the encryption of subcircuits, but not hierarchical designs.