There is no upside to using the Jepson format, and there is a significant risk. The risk is that anything in that preamble (before the "wherein the improvement comprises:") will be considered to be part of the admitted prior art.
There is really no cost to writing the claim in the traditional form, reciting the existing elements, and then the novel improvement as the final clause.
I don't know any US attorney who would use a Jepson claim. They are used quite often overseas, though, because some countries do require identification of the novel subparts of the claim.
A note for the readers:
A Jepson claim is in the format of:
A preamble comprising a general description of all the elements or steps of the claimed combination which are conventional or known, followed by a phrase such as “wherein the improvement comprises,” and the novel elements. So for example for an improved rocking chair it might read:
A rocking chair with a seating area, arms, a back, and curved legs, wherein the improvement comprises: a stopper at the end of the curved leg to prevent tipping over backward.
It is an easier format to write, but a riskier one in almost all circumstances.