Direct sequencing of her genetic code would give the most theoretically predictable results, if not at the very least the most permanent results. It's always possible that either of the two options could fail thanks to any number of immune system responses her body might have, but altering herself on the genetic level only holds the weight that what she does is permanent... and considering such a thing is exactly what she wants, it's not as if that's a downside, now is it?
Bulma quickly begins to scrawl down the various theoretical ways she would have to alter her DNA in order to garner what she's looking for, which is marginally increased body durability and stamina, and a healthy promotion of muscle growth through altering her metabolism and appetite. By increasing her durability and stamina, she'll have an edge on the humans since she can push her body far harder for much longer during trianing.
Sure, she may not be able to challenge the likes of a Super Saiyan, but it's not like she can't coerce Goku into teaching her the Kaio-Ken technique if she's really strapped for power at that point. Regardless, she eventually has a very rough idea of what she has to do to her genetics, and with that she decides to get to work.
"Who knew I'd ever use this old thing again." Bulma pulls a tarp off of a tall object in the back of her lab, coughing and choking a little as dust fills the air. When the dust clears, she's face to face with some sort of walk-in chamber. "My old genetic re-sequencer, my pride and joy." You see, Bulma has long ago cracked the ability to alter genetic code, but when she took some time to consider the implications, the scientist simply scrapped the project, kept it unknown, and stowed the machine away never to be used again.
'Now I'm planning to use this for the very reason I scrapped it... its ability to produce soldiers that surpass the likes of our current superhuman fighters...' Really, Bulma can't help but feel proud of this! Who knows, maybe she'll play with the portion of genetics that controls aging as well. Some elongated youth never hurt anybody, right?
The blue-haired genius clears the area around the sequencer, hooking it up to the water, coolant, and exhaust pipes that go through the entire building. Next she runs a quick diagnostic test just to make sure everything is in working order. Before long, the machine is on and ready, and Bulma is entering the alterations she'll need done to get genetic code.
"Aaaaand there we go!" With a press of the Enter button, the machine confirms the changes, and the door to enter it opens. Bulma steps in, clad in a skintight black bodysuit, the bodysuit littered with small holes. Standing dead center in the middle of the small chamber, the door seals shut and the old re-sequencer begins to whir.
The lights within go from normal to black lights, and small needles extend from every wall. Shivers run down Bulma's spine as each needle pokes into one of the many holes in the suit, while many needles go directly into her bare skin from the neck up. Small injections are occasionally let out, as the light changes gradually between different types of mild radiation.
It feels like an eternity for Bulma, but soon all the needles retract, and the machine whirs to a stop. The door opens and Bulma steps out... looking down at herself, Bulma feels very...