As Me... says, some inexpensive brands may have poor binders or compression of the tablets so that they fall apart too quickly. When I used GLB Trichlor tablets in my floating feeder 6 years ago, they lasted around 5 days. They will probably dissolve more quickly in an inline chlorinator though it depends on the setting (flow rate through the chlorinator) you use. Bioguard is a name brand. See this post
for a list of manufacturers and brands. The big 3 are Chemtura, Advantis and Arch. I don't know who Leslie's uses.