I would love to get into a huge debate about this... but will keep it simple.
First, ask yourself these questions:
A. Is it strictly financial or are their other technical reasons for looking at other options?
B. Are you happy with your current solution, vendor relationship and support?
C. Does your current vendor know the answers to A and B?
I can't share the all the details, but can tell you that looking back were unpleasantly surprised with the project, hidden expenses and costs to get what we needed to meet backup requirements and business expectations. Funny thing is we now have Avamar, EMC NAS, IBM DS8300, XIV, VTS, Tape and still need TSM.
My only suggestion is to get IBM / NetApp and EMC engaged in the decision process and select one as a strategic partner to move forward with.
We now know IBM will do everything in their power to keep you as a client and hold true to the commitments they make. Sometimes they just need a wake-up call or a meeting of the minds. Set up a meeting with the management team of your local IBM software and hardware account reps. It can only benefit you / your company in the long run.
Finally, regardless of who you select I would be curious to know if you could answer "Yes" to any or all of the following?
1. Does the solution meet your business needs, expectations and technical requirements that were originally discussed with the vendor?
2. Does the budgeted solution price align with the actual total expenditures (after year 1 and year 2) ?
3. Where all the costs for services, support, features or upgrade known upfront?
4. Do you value your technology provider as a strategic partner or trusted adviser?