The issue that a lot people don't get is that historically leaving money in cash, you are bound to loose money in real terms over the long term as others have pointed due to inflation. Any investment or fund offering higher return than cash carries risk, risk can be great in that it can be opportunity to make a well above inflation return, it can also be bad in that you risk loosing some / all of your money invested.
So my thoughts ideally you would want to spread you risk (both the good and bad side of it) around in terms of both different types of funds, different asset classes (property, share, bonds, gold, collectables). Having done that you can then work out the most tax efficient and cost effective way of managing things. Also worth considering time / effort - managing land property can be problematic, paintings / collectables need storing and insuring etc. etc.
You also might want to consider how liquid the investment is, for example on the forum we deal in domains so understand the difference between trade and end user pricing, but generally if you need to raise funds you can do so quickly it just a matter what sales route you take as to what you get. If you own property it can be sold might take several months - in a slow market longer etc.
What is really disappointing for me is to see lots of people suckered into investment schemes that are heavily marketed (which means those costs are paid out of investors funds) in the likes of self storage units, solar energy schemes etc. airport parking places, hotel rooms. Often getting folk to transfer their existing pensions (which are probably in half decent funds) into these schemes offering supposedly inflation busting returns which in reality are not guaranteed, and more often than not the money disappears in eye watering fees, management costs and probably a totally dud underlying investment. Folk because they don't understand how their existing investments are allocated then make a life changing (in a bad way) decision.
So my closing thought is a general warning - if something you are offered looks too good to be true it probably is!
JohnP