In my opinion, a Block is a far better solution than a Group for what you describe.
If you put things into a Group, when you want to reuse that selection, there's no command to put in another like it, so you need to select the Group, and use either COPY or clipboard-Copy/Paste to make another. If you Copy the Group to the clipboard, you can Paste it in as many times as you want, but you lose the clipboard content when you close down, so tomorrow you would need to Copy the Group again. And you would need to find the original Group to select it as a Group, because the copies of it that you Pasted in before will be in independent pieces, not grouped. And for multiple reuses within one editing session, you wouldn't be allowed to use Copy/Paste with anything else that would replace what's in the clipboard. But a Block you can INSERT whenever you want -- you don't need to have one available to select for COPYing or Copy/Pasting [but you can still do it that way if you want], it's equally available after you have closed and re-opened the drawing, other usage of the clipboard won't interfere, etc.
Also, pieces in a Block definition that are drawn on Layer 0 will come in on the current Layer whenever you INSERT the Block, unlike pieces of a Group that you COPY or Copy/Paste. So you can reuse the same content on different Layers.
And you can scale a Block differently in any or all of the three axis directions, upon Insertion or afterwards, whereas with a Group that you Copy/Paste, you have a scale option in Pasting, but only at equal scales in the three directions. And if you want to scale a reuse of the Group afterwards, you'll need to select the pieces independently, because they won't be grouped.
If you want to change something about the pieces, with a Block you can edit the definition and all Insertions of it will be updated, whereas with reuses of a Group, you would need to go around and find all of them and make the same change(s) separately in every one.
Kent Cooper, AIA