I'm a big fan of bodyweight training and if you stick to the bodyweight training, you probably don't need any of those until you can do 10 pistols.
With that in mind, I would get pull-up bar or gymnastics rings first.
If you have them or easily access them, I think either kettlebell or vest is okay.
BTW, weight loss is more about diet than exercise, and the major role of exercise on weight loss is increasing metabolism by building muscle rather than burning calories directly.
Please keep in mind that the strength (or muscle) you can build with only one kettlebell is very limited especially if you are a guy.
If you are going to add more kettlebells later, kettlebells can be a good choice, but if you are a minimalist, vest would be better.
Last edited by vincebae; 07-02-2013 at 10:35 AM.
what is your current workout routine? i'm voting for the weight vest. its 1000x more functional than the kettlebell. you can add the weight vest to every single bodyweight exercise that you can do. you can sprint with it. you can hike with it.
a kettlebell is decent for a few things, but is probably the single most over-hyped piece of fitness equipment on the market today. its a neat addition to a solid home gym, but 1 kettlebell isn't going to get you that far. definitely the vest.