I was playing around with a few laptops and it seems that allowing speedstep in the bios always makes the computer run slower... was wondering if anybody might know why
That's the whole point of Speedstep. Slow down the CPU when it's not being used to save power and reduce heat output. It increments the speed up as CPU demand increases until the max speed is reached.
System responsiveness is really where speedstep can be seen negatively. Intermittent bursty workloads can be helped by disabling it. Here's a recent article talking about improvements and a renaming in Skylake CPUs.