Done properly, both are good enough. However, the proper patch from a tire shop would hold as they do seal it after the plug is in.
I see those DIY outside plug kits all the time. If I'm in there doing a tire repair, I usually put a bit of sealant on it from the inside to help it not leak in the future.
If you can, bring it to the tire shop and have a proper patch and repair done. In an emergency though, itll be ok