Nowadays , many software programs are available for primer design. For many researchers, is always a question that which one is the best for primer design?
i usually use primer blast from ncbi and primer3. Primer3 is easy to use but you have to analyze primer it suggests because sometimes the primers are unspecific.
I would add that primer BLAST is particularly effective at designing isoform specific primers because its is part of NCBI and thus can manipulate splice form sequences very effectively
If however you already have the sequences to place primers in then Primer 3 and primer BLAST are equally effective