I had always seen the Deltran Battery Tenders advertised on car shows on TV, but resisted buying one because of the high price. I could buy a 15 amp charger with 100 amp boost function for less. Besides, my summer car, a 1985 Camaro, had a grandfathered lifetime warranty battery from Canadian Tire that they would replace for free anytime it died (they haven't sold those for years anymore). It seems to me they don't make batteries the way they used to because in recent years in recent years the warranty replacement batteries failed earlier and earlier. The second time I wasted a day getting the battery replaced in the spring. I decided to get a Battery Tender Plus. I've never regretted the decision because the Camaro would start right up in the spring.
I also have an electric start riding mower, so I'd remove the battery during the winter and put it on the Battery Tender on and off so I wouldn't have to charge it in the spring. I figure that is less stressful on it than letting it die and using a regular charger. This winter I was in the hospital for hip surgery, so my daily driver was sitting. That's when I bought a Battery Tender Junior on sale. As far as I can see, the BTJr is .75a vs 1.25a and doesn't have temperature compensation.
From what I recall, the Deltran Battery Tender was the original and it's been around a long time with good reviews. Once when I took my dead battery back to Canadian Tire I asked whether a Battery Tender would be what I need to keep it from dying over the winter and was no. That was before the sold the BT and those counter guys don't know everything. Now there are several battery minders on the market. I sure wish there were a website comparing them all. Meanwhile, I'd stick with the original. You might save some money on something that purports to do the same thing, but when you consider the time and money wasted on a dead battery, it's foolhardy to cheap out.