Switch hitters need to be very good from the left side, because that is the side they will be hitting from 70%-75% of the time.
Example: A switch hitter with 400 at bats.
Hits .350 from right side and .250 from left side = .275 batting average.
Hits .350 from left side and .250 from right side = .338 batting average.
Of course, these are approximate numbers and don't tell the whole story. Typically, most switch hitters will have more power from one side or the other (usually right side). This is especially true with young players.
FWIW... Over the past 10 to 20 years, the number of LH hitters has greatly increased... To the point that good RH hitters are becoming more valuable to recruiters and scouts. No one wants a line up that all hits from one side.
As always if a hitter is good enough, it doesn't make much difference. Checking the draft results will show that the best hitters get selected early no matter if right, left or switch. Obviously, most of those are not switch hitters.