This isn't an answer - because the correct answer, if there is one, will depend on your circumstances and what exactly you need to do with all that data - but here are some things to consider:
- If you have your own server, then in addition to the CapEx to buy the system you must budget for somebody's time to maintain it (maybe a group member, if somebody has the requisite knowledge, or maybe somebody from your institution's IT department), electricity (if you pay for that), backups, and so forth. (do not neglect backups - if your main need is storage, this may nearly double the cost)
- If you use a cloud facility then you have all OpEx and no CapEx - but the operational costs will be substantially more.
- In my experience looking into this for compute-based HPC tasks, if you can't keep your own system busy then it's often better value to use cloud offerings, during the life of the project. If your main need is storage, this may well not apply.
- Once the project has finished, if you have bought a server then you have an outdated server that you may, or may not, be able to usefully repurpose. If you have used a cloud system then you have nothing.
- Consider transfer speeds to/from the storage. If your data and your processing are both in the cloud that's fine, but don't plan on copying tens of terabytes between local and cloud systems on a regular basis.
So far, those are considerations that apply everywhere - not just to academic projects. But here are some additional considerations for research:
- If the need is mostly for storage and not serious computation (not clear from the question) then up to 100Tb isn't that much storage by today's standards. It's more than a university IT department is going to offer for free, but you might be able to pay them out of project funds and not have to worry further about it. That way you get a resilient system that's looked after by professionals within your institution. They'll probably be buying the same hardware that you'd be buying yourself, so this isn't a cheap option - but it may be a good one.
- Consider whether, at the end of the project, you will still need to store that 100Tb - or whether the archival need is less. Consider whether, and how, this relates to any funder data archiving policy, and/or any instutional archive facilities.
- Some funders like to be able to take pictures with a thing that they bought (though you're probably talking about bigger computers than this before that kicks in). Similarly, some funding streams will only cover CapEx and some will only cover OpEx, so this may be the deciding factor.
There are probably some other factors that I haven't thought of - if you've thought of one - especially for the second section - that you don't think is worthy of its own answer, leave a comment and I'll edit it in.