The Netrunner rules suggest playing with Jinteki as a first hand, but I have heard that is a bad starting deck. Which should be used for a starting deck for introducing someone to the game? And which should be used for someone who has only played as the runner but not the corporation?
Jinteki is a bad choice for first time corp player because, with only the starter set, the deck does not have enough ways to generate credits. Having no money means you cannot do much and usually leads to the new player not having fun. If you are trying to teach someone, fun is the whole idea, so this is obviously counter productive.
With core set only decks, I would do Weyland vs Shaper. Both play styles are easy and both run pretty rich.
If you are up to building decks specifically for teaching there are some better options.
Here is a board game geek thread that has a lot of beginner deck suggestions, though some decks here use more than just the core set. Here is a reddit thread that has beginner decks using only the core set.
FFG has actually released decks that it thinks are the best for teaching. These decks leave out a lot of the more complicated mechanics such as Trace. They focus on both players setting up their side of the board quickly so there is almost always an "end game".
Note that the Demo decks clearly don't follow normal deck building rules. They are purely for teaching. In addition they only require 6 points to win by agenda points.
Jinteki - Personal Evolution Agendas: 3x Priority Requisition 3x Nisei mk2 1x Unorthodox Predictions Operations: 3x Hedge Fund 1x Restructure 2x Trick of Light 2x Neural Emp Assets: 2x Melange Mining Corp. 2x Private Contracts 2x Snare! 2x Project Junebug ICE: 3x Wall of Thorns 2x Bastion 2x Wall of Static 3x Enigma 3x Chum 3x Neural Katana
Shaper - Kate "Mac" McCaffrey Events: 3x Sure Gamble 2x Modded 2x Freelance Coding Contract 2x The Maker's Eye 2x Infiltration Resources: 1x Professional Contacts 1x Aesop's Pawnshop 1x Ice analyzer 2x Armitage Codebusting 2x Public Sympathy Hardware: 3x Akamatsu Mem Chip Programs: 2x Magnum Opus 1x Net Shield Icebreakers: 2x Battering Ram 2x Gordian Blade 2x Pipeline