WN gives you free same day standby after you reach A-list (25 one-way trips in the year). Ask them for a status match or fast track challenge before you start. I would be reluctant to burn my once in a lifetime AS status match on anything less than 75K (top tier, includes 4 giftable and quite usable upgrades).
Consider earning top status on WN in 2019 then matching to AS or UA for 2020.
Same day standby on WN is only for earlier flights. It's quite inflexible. Free confirmed changes to earlier or later flights is much more valuable.
RE: AS, I disagree. The difference between Gold and 75k on AS is minimal. The real value is mostly at the Gold level. Gold gets you all change fees waived (which is huge), a 100% mileage bonus (which is also huge), and 4 upgrades which have limited value (due to minimum K fare required required for use, the fact that they can't be waitlisted, and the fact that when U space is actually available at booking, it's a sign that they expect to have plenty of first class availability and you are likely to get a comp upgrade anyway as Gold).
At 75k that bonus goes up to 125% (which is nice but not that much more than gold) and a 4 more upgrades (which still have limited value). Earning 75k is huge (because you get a 50k RDM bonus) but you don't get that for status matching. The marginal value of actually having 75k (instead of gold) is far less than the value of that 50k bonus.
There is a lot more discussion about this on the AS forum (where it belongs) but to go back to the OP's dilemma, I would not suggest choosing WN over AS simply to avoid "wasting" the status match. Pick up the AS credit card as well, put all the AS flights on it, and In that one year as AS MVPG taking 2x short-hop segments per week, he'll earn 100k miles from flying, 40k from credit card bonus, and maybe another 30k from the spend on the flights --- that's 170k miles. Considering the great AS partner award charts, and the stopovers allowed, that's enough (for example) for a business class 3-city trip through Asia (2 one-ways with a stopover in each direction, on different partners -- eg CX and JL) and enough left over to be half way towards the next round trip.
On WN he will earn enough to suffer the indignity of a few more WN flights.