Every company should buy the least expensive product that satisfies your requirements. The first place to start is to define your requirements. In many cases we have found that most companies do not have the internal expertise to do this well.
At a minimum your prospective software vendors or consultants should assist with you with this process.
Selecting new software is costly, time-consuming and complicated. It's difficult to meet the needs of every department and determine true capabilities versus promise... especially from multiple sales presentations and impressive proposals.
Welcome to the world of ERP - and please remember buyer beware and please educate yourself! We would recommend you consider the following:

The actual software cost will be a minor portion of the total installed cost. On top of software license cost there is outside consulting and training as well as man years of internal staff time. Focusing solely on software costs may prove to be false economy in the long run.

The technology base is a significant factor - older technology has a limited life.

You are about to enter a long term relationship with your software vendor - look closely

Specify the consultant(s) assigned to your project - what is their background - are they an employee or contractor?

Document all vendor answers to your questions and have this form part of the contract

Ask to vendor to provide a detailed project plan for the project including what resources you need to supply
After the project ensure your relationship is managed fairly. At the start of the project you will control the levers of internal staff allocation and invoice payment. After you go live the power base moves entirety to your vendor. You will have problems ranging from minor (additional training) to major (your system is down). You need to make sure that you can call on your vendor for fast service at a fair price.