Seed is usually considered to be a generator, because it serves a similar function and is among the generators which can be chosen at the start of the game. However, it is not strictly a generator, as it does not increase your available PWR.
In most loadouts, Seed effectively gives you one “free” hack per turn. Good programs to pair with Seed are those that cost 3–4 PWR and can be used every turn, such as Lockpick 2.0, Data Blast, Oracle or Golem. In this case, Seed is more efficient than any other generator (except, in very specific situations, Wildfire).
However, when using Seed as your starting program, Consoles will often be your only source of PWR, so you have a fixed total supply of PWR for whole mission — you will need to use it carefully. After your one “free” hack each turn, you will usually need to use programs with low PWR costs, such as Parasite, or Rapier at alarm level 0. So, when playing with Seed you will want a mixture of programs to use “for free”, and programs which cost little or no PWR so you can hack more than once per turn.
Seed only reduces the PWR cost of programs, so it does not pair well with items, weapons or augments that consume a lot of PWR, particularly Volt Disruptors. Seed can also make it difficult to complete the Power Relay Station side-mission, which requires saving 15 PWR. It is often worth supplementing Seed with additional power generation from programs such as Emergency Reserve, augments such as Distributed Processing, or Portable Servers, so that you will have PWR for other purposes.