Did you have a particular one in mind? Most people tend to go with TacStar or Mesa, but more and more people (including myself) are being converted by bbb to the S&J Velcro ones (or similar).
I have lots of experience with the TacStar and Mesa but I only recently slapped on the S&J velcro one but in case you are interested and since I am bored, here is my personal review...
TacStar - inexpensive side saddle, build quality is what you would expect for the price, which means not as good as Mesa but it's also half the price. People claimed to have an issue with shells coming loose under recoil but I found the TacStar to have the best retention of all the ones I tried. It was in fact too tight when I first got it but it broke into be a perfect level of retention. My biggest complaint is that it seems quite bulky... this and the not so great fit and finish are what convinced me to try Mesa. Some people don't like it because it's plastic but this doesn't bother me one bit just like Glocks and M&Ps don't bother me with their plastic

. Also, you can't see the serial number of the shotgun with the side saddle attached... can be a pain in the ass if you ever don't have hex keys with you and need to see the serial number for some reason.
Mesa Tactical - fit and finish is super, it's made of aluminum, a lot sleeker than TacStar, looks way ###ier in my opinion, is still fairly lightweight, and you can still see the serial number with it attached. Does cost twice as much as TacStar and while I feel the material and workmanship are at least 2 times better, I did not feel like it functioned any better so it was a disappointment.
S&J Velcro - First of all, it's very inexpensive... for the price of one Mesa, you can get 4 of these ones and use them all on one shotgun because it is detachable velcro. Build quality is excellent, don't let the fact that it's nylon/elastic loops deter you. You can cut out pieces from the velcro to allow the serial number to show when the velcro backing is attached. I have not shot many rounds with it on yet so I can't say for sure on shell retention but no one on the forum really seems to have a problem... so far so good for me too. The only
POTENTIAL negative that the velcro backing attaches to the shotgun with an adhesive (it's basically a sticker). I am anxious to know how durable this is and if it will do any damage to the shotgun's finish when I remove it. I believe badboybeeson did testing on it and found it was just fine but contact him if you want to make sure. He is awesome to deal with.
Hope this helps.