Can anyone tell me if what type of ice-breaker you're using affects whether or not it can overcome the strength of ANY type of ice it encounters or does the type of ice-breaker you're using only matter as far as whether or not it can break the corresponding type of ice's subroutines?  As I'm understanding the rules, type of ice-breaker does not matter as far as overcoming the STRENGTH of any given type of ice, but it DOES have to be a match where subroutines are concerned.

Any clarification on this issue would be greatly appreciated!

Thanks!

You need the strength only if you want to break the subroutines (not all ICE can end the run, so you might not want to break all subroutines). So, while matching types is in theory irrelevant to increasing strength, in practice, you'll only increase strength when types match (otherwise you're wasting your precious credits).

For example, take Hunter: it is a stength 4 sentry with a subroutine that make a trace3. Since the routine doesn't end the run, you have 2 choices (with both letting you continue the run). Either breaking the subroutine or letting the corp attempt the trace. Assuming your killer (the icebreaker type that matches sentry) program is Ninja (this would be the cheapest), you're going to have to pay 3 credits to increase Ninja's strength and 1 credit to break the subroutine. If let the trace go off, you will need to pay 3 credits minus your link value plus whatever the corp pays to make the trace fail. You can also let the trace succeed and remove the tag later for 2 credits and an action (risky if the run is your last action). But if you want to let the trace go off (or if you can't break the subroutine), you don't need an icebreaker of any type with strength 4 (before of after increasing).

You are indeed correct. For example, Ninja (Sentry Killer) could actually affect Enigma (Code Gate) were it not for Ninja's subroutine-breaking ability being specific to sentry subroutines.

 Related question:

So for what effects does an Icebreaker have to match/beat the target ICEs strength? From what I've been hearing, Wurm has to match/beat to use it's strength lowering effect but Femme Fatal does not for its secondary bypass effect.

Toloran said:

To use its abilities that affect the ice's subroutines etc. Femme Fatale is different as she bypasses the ice altogether so does not need to break its subroutines to get by the ice that was selected when she was put in to play. Wurm has to equal the strength first as you can only interact with a piece of ice that you equal or beat the strength of.