What are they for ?
If you are using them to support / retain a lower denture, then regular are best, but mini's are better than none at all.
If they are to replace teeth , then mini's are not recommended. At your age, regular are best -- research goes back 40+ years with tremendous sucess (90 + %), and will serve you best. Mini's ok for lower denture improvement, but not enough longer term research for other use.