Unless your contact gives you express permission to contact her on her cell phone, or if you’ve moved past the “contact” phase and into the friend zone, email is the more professional choice. (You’ll know you’re in the friend zone when you can imagine the person sharing Sunday brunch with you or introducing you as “My friend Jane” at a mixer, not “Jane Doe, who works at CAA.”) It may seem silly to put so much thought into the way you reach out, but trust us: A little professional decorum can go a long way.
When you text someone, you’re interrupting them. Imagine your contact is in a meeting with her cell on vibrate and she feels it buzz. She pulls out her phone to discreetly check -- is the message from her boss or a family member reaching out for something important? Maybe she excitedly hopes it’s her Tinder date from the night before actually not ghosting her. When she sees your name -- or more likely, a number she doesn’t have saved in her phone -- she’ll probably roll her eyes and feel bothered, even intruded upon. And it's worse if your text comes in after work hours or in the middle of the night. You should never interrupt a contact's personal life with work-related text messages, especially those asking for advice or favors. If you're a pest via text, your contact isn't going to want to help you in the future. Plus, text messages are hard to track in the first place -- if your contact isn't near her work computer when one comes in, she's probably going to forget to put your request on her to do list, and you're back to square one.
An email, on the other hand, doesn’t disrupt anyone’s flow, nor does it warrant an immediate response. Your contact will get your email confirming your meeting or asking for a favor when she chooses to check her emails and will respond when she has time. Instead of feeling harassed or bothered, she’ll feel nothing at all, because the exchange will be normal and professional. If you haven't met, she’ll approach your meeting with an open mind, and if you have, she'll be a lot more likely to help you with your job search. Plus, you'll have an easy thread to use for follow-ups and thank yous -- what can be better?