I have had both in kitchens and the upper particle boards would not carry the weight of the items. I am an extremely organized person especially in the kitchen so the cabinets should of held. I now have the better cabinets with weight from Corning ware and many glass dishes, it should be having an issue and is is not. I would with any cabinet add a nice waterproof liner.

in a flood, both plywood and particleboard cabinets get ruined....For base cabinets only, not too much difference. The particleboard could settle more if they are not set level, causing countertop issues (so make sure they are set level and well supported beneath). The sink cabinet will take a lot of the abuse - any water that drips below the sink will cause the wood floor to swell - as the above poster mentions, add a waterproof liner. Rev a Shelf makes some that are like car floor mats with a tall edge to contain any spills or drips. I don't believe that particleboard is stronger - especially in upper cabinets where all of the weight is hung on several screws...but as you said - lowers only - I say go for it! Robert

There are many different grades of particle board depending on the manufacturer. if you are happy with your cabinet maker and the lifetime warranty is from the manufacturer, there shouldn't be a problem

Honestly I think a lot of it has to do with the budget and overall quality of the brand. Are you looking at custom cabinets?

As with all projects, they come down to expectations and budget. How do you expect those cabinets to perform? If you want to insure against issues that could develop over time and want to see those cabinets last a long time, then you should invest in plywood. If you are after aesthetics, and won't be giving the kitchen heavy use and can insure against fluctuations in humidity, particle board may be an appropriate option for you that would save some in the budget!
Thanks, Brenda