As the market gets younger and younger people will text more. If you're client is a "texter" match it. If they are "phone call" person match it. Do what your client likes and needs. You have to be able to change with the times.
Also I agree that all contract communitcation should be in e-mail form and/or writing so you can document it. BUT for people that don't know this I'd like to share a bit of info. There are APPS that can take a whole text conversation 200+ messages, put them into email form and email them to yourself. This will give you the phone#, dates, times and then you have all that documented. I actually do this with my tenants and clients.
Like I say CYA ... Cover Your A**