There are a few differences between ACH and Wire transfers that should be understood before making a decision. 

ACH uses a batch process that allows a large batch of transactions to be handled at once, hence, why these are usually free of charge or have very low costs. Wire transfers, on the other hand, are individual transactions handled by an individual request, and are more expensive to use due to the increased processing costs that come along with them.

There is also the settlement period, ACH transfers typically take one business day to complete. Wire transfers move funds from one bank to another within one business day usually, but sometimes may need human interaction with a bank employee to finish the process. Learn more about settlement period here.

Both services are considered safe and trustworthy. Each use advanced security protocols to keep data private, and prevent against fraud.

In GrabrFi ACH transfers are free, unless you choose same day ACH, which will cost you $1.

While Wire transfers will cost you for domestic Incoming wire $5, and for domestic Outgoing wire $15. See here the full schedule of fees.