If you own one of the ported Ultra subwoofers from SVS, at any time while you own it, you can change your mind about whether you want to run it ported or sealed, as it comes with blocks for the ports. And if one wishes to run it ported, one can leave all of the ports open, or block one or two of them for different tunings. You can do this after the 45 day trial; it is a feature of the subwoofer. But with the sealed version, it is just a sealed subwoofer. So after the trial period, if you have the sealed one, you just have a sealed subwoofer. But with one of the ported Ultra subwoofers, you can run it either sealed or ported.
Additionally, after the 45 day trial period, when one has settled into using one's subwoofer, one can easily and relatively inexpensively upgrade if one bought one really good subwoofer instead of two lesser ones, by simply buying another one. (With two lesser ones, one is likely going to be selling off the pair one has at a loss, and still have to pay the cost of the more expensive subwoofers.) It may well be that one is not going to get a windfall within the next 45 days, so it may be that one will have to wait beyond the trial period to upgrade to 2 Ultra subwoofers.
Of course, if one has a lot of money now, one can buy a pair of Ultra subwoofers now. But that is not the situation described by the opening post.
Also, the biggest perk of going with SVS is that one gets a great subwoofer for the money spent. A free trial of garbage would not be worth taking.