Thank you for your question.Easy answer: solid silicone.You want solid silicone for two reasons. The proper shape is the first reason. The solid silicone implants that are designed for the buttocks are the proper shape for the buttocks, as opposed to the cohesive gel breast implants which are designed for the breast shape. The second reason is the rupture rate. The cohesive gel implants would likely also have a high rupture rate from all of the pressure if you sit down forcefully.
In my experience high cohesive gel butt implants, not breast implants, the ones designed specifically for intramuscular butt augmentation, feels and looks way better than solid implants, and as they are design for this area they are strong enough to hold the pressure without rupturing. The only problem those implants have is that they have not been approve by the american FDA so you will not find them in the United States.All other countries of the world prefer this implant to the solid ones, And i'm completely sure that it will happen the same that happened with silicone breast implants. After of couple of year, FDA will approve this implants and will be the preferred implant Nationwide (USA). Right now if you want to have your surgery in the US the only option you have is solid silicone, if someone offer you a cohesive gel there, do not accept it, it probably is a breast implant and those do not hold the pressure of the butt. Best of luck,