It's been my personal experience that any admittance of porn/mb within the past ~2-3 yrs is considered a deal breaker for most LDS Single Women (btw, this never happens in reverse). A few years ago, RS President Julie Beck advised women when they 'find out' to raise a red flag and stop the relationship.
I definitely think practically speaking that visual porn (not to be confused with books) is the bigger sin for most LDS women. (even though most will not admit this) (There is also a case to be made that theologically masturbation/porn has the larger penalty as well.
What's worse? 1 yr excommunicated OR the greater part of 10 years feeling unworthy to take sacrament. Additionally, Some bishops penalize you for 6 months (no sacrament/no temple/no priesthood privileges)
Consider however that you can be worthy of the sacrament/temple recommend, but still be served divorce papers (women file divorce papers 70% of the time btw) or be rejected for marriage... because of admitting that you looked at porn within the past year.
Most women I know wouldn't think twice about marrying a baptized David Beckham (or similar) (regardless of his sexual past). Surprise, Surprise - it all just magically washes away... when romance is in the air... women make romantic relationship decisions based on emotion/feelings. (and considering the overall package - height, bank account, etc..)
So while adultery/pre-marital sex can get you excommunicated, Porn earns you the eternal hatred from the tribe of lds women.
So even though you could be an otherwise GREAT guy (virgin, temple recommend, boy scout, missionary, never missed a tithing slip, great career, and serving in your ward) most LDS women will pass you up (or divorce you) if porn is brought up.
Ultimately, the semantics of sinning is boring (It's all sin!) and what is interesting (at least to me) is seeing heroic couples learn how to build healthy relationships through all of this.