I had both at the same time for several years. Depending on the rest of your system and your hearing acuity, it will be a slight difference or a revelation. I definitely preferred the squared version but unless you had both and were able to A/B them quickly, you might not be able to reliably tell the difference on most material. For movies the difference seemed even less noticeable.
On some of the reference material the differences were more distinct, particularly at lower volume levels and in the upper frequency register, although the bass sounded more realistic if not a little less full when hooked up to speakers capable of accurately playing low frequencies.
I recently sold them to fund the purchase of some new 7B's to go with a recently acquired pair of Middle T's. The 4 was more than capable but I decided to treat myself and down graded my multi channel system to spend more time and money with 2 channels.
If you will always wonder what you may be missing out on, I would go with the squared version. Depending on where you are coming from, the 4bsst may be a revelation in and of itself.
