Years ago, I had a pile of magazine subscriptions. I slowly began to realize that I wasn't taking time to read them all and they were just piling up with the unread newspapers. Over the years our subscription list has become shorter and shorter. At the same time, many of the various retail establishments I frequent, such as Sam's Club and Costco, began writing magazine length advertisements and sending them out to customers. We also started getting "free" newspapers delivered to our driveway, several times a week so the amount of paper we get is actually seeming to increase.
So the heart of the question in this post's title is the utility and amount of use of each of the subscription sites. This is a highly personal decision. I always suggest that before subscribing to any online service that the potential user investigate the website carefully and, if possible, work with the website at a Family History Center where many websites are available for free.
One important factor in considering any subscription website is whether or not the site has the records supporting your particular area of research. Sometimes determining which records are actually available on any given website is difficult, although, if you persist in investigating the site, you can probably get a list of some kind. There are options with some genealogical websites to "pay as you go." I have found that this is an option only if you are reasonably sure that you will not find more records on that same website. It is not unusual for the fees from "pay as you go" to exceed the amount of a monthly or yearly subscription.
One real-world factor is the amount of money you have to pay for subscriptions of any kind. I frequently hear stories of genealogists who travel great distances to do research and find that the records they are seeking are no longer available because the records have been digitized and are available online either for free or in a subscription website. Even the most expensive annual fee for a subscription website is only a tiny fraction of the cost of traveling across the country or around the world to do research. I would certainly exhaust all of the possible online sites before undertaking an onsite research effort. However, there are some places where visiting the site is less expensive than the alternative. This is true, for example, with the Family History Library in Salt Lake City, Utah and other such centralized genealogical libraries. No subscription is a substitute for a visit to the Family History Library.