I'm not talking lifestyle mini-cubes, this is about real bookshelf speakers.
A good immediate example (because of clearance sales) is the Wharfedale Diamond 10 series.
If you like the Wharfdale sound and are looking for a BS speaker, you can currently get the 10.1 at $200/pr (MSRP=$350) and the 10.2 at $275/pr. (MSRP=$450)
https://forums.audioholics.com/forums/threads/any-holiday-sales-thread.77597/page-47#post-1224343
So which to buy?
It seems reasonable to think that the 10.2 is the better option! You are getting a great discount either way and figure with the money you are saving, you can "splurge" for the 10.2's! However, that might not really get you the best sound!
The reason is that in a two way speaker, the designer is playing a game of how much bass vs a smooth transition between the woofer and the tweeter.
The major factors are:
1) How low can the tweeter go before it becomes distressed? You can only expect a 3/4" or 1" tweeter to extend so far down into the mid-range frequencies before it is pushing its capability.
2) How high can the woofer go before it becomes distressed? The larger a speaker, the less capable it is of extending into the upper midrange.
3) How much bass do you want from the speaker? Item 2 would suggest a smaller woofer is better, but that limits how deep the speaker will go.
So, the 10.1 has a 5" woofer and the 10.2 has a 6.5" woofer. Both have 1" tweeters, both cross to the tweeter at 1.8kHz, and both are rated at 86dB Sensitivity. The 10.1 is rated at 48Hz - 24kHz and the 10.2 is rated at 40Hz - 24kHz.
Now, let's look at the Tower version of this speaker (Diamond 10.7, MSRP=$1300/pr. on sale for $700/pr). It has the same 1" tweeter and the same 6.5" woofer as the 10.2. It also adds a 2" midrange and a second 6.5" woofer (without the phase plug and with a low pass filter at 150Hz).
The most relevant aspect of this, in my "armchair analysis", is that Wharfedale chose to use a good chunk of the tower's additional cost to add a 2" midrange (with additional crossover) which takes over the duties from 850Hz to 4.5kHz! From this, it seems likely that the transition from 6.5" woofer to 1" tweeter might not be so smooth as it ideally could be!
A 2" mid-range at 4.5kHz might be the ideal, but it is an easy bet that a 5" woofer will better blend with a 1"tweeter than a 6.5" woofer!
The benefit of the larger driver is additional bass: 40Hz instead of 48Hz. However, if this is a 2.1 system and you cross at the traditional 80Hz (or higher), I don't believe the 6.5" woofer adds anything audible over the 5" woofer!
Consequently, the 10.1 is likely to sound better in a 2.1 system.
(If it were a 2.0 system, the added bass may well be worth a somewhat less smooth transition)
As a contrasting example, lets look at the SVS Ultra Bookshelf. Here we have the same: A 6.5" mid-woofer crossed to a 1" tweeter... but at 2kHz!
However, when we look to the tower, what did they do? They use the same 1" tweeter, use dual 6.5" mid-woofers as midrange drivers, and add dual 8" woofers!
Obviously, they felt like the transition from 6.5" to 1" was good enough for their flagship speaker. If you consider that the street price is roughly 2.5 times the street price of the Diamonds, I would speculate that the quality of the Ultra 6.5" and 1" drivers allow them to more successfully blend/crossover.
Disclaimer: I am no speaker designer, and, as compared to many members of this forum, am quite ignorant of Speaker design concerns. However, from a pragmatic/generalized standpoint, I think my statements are valid and I welcome any corrections, education, or additional information more knowledgeable members provide. What I am describing is my own thought process which may be a useful stepping stone for those who have not yet obsessed much over such matters.
