Interesting topic. I like to consider these sort of things, and am always interested in how other people approach them.
Personally, I like individual basing, and I like casualty removal, and this is for 'massed battle' games.
I realise I am going against current trends here.
My reasons are...
1 - I like to see units visually reduced in size. I don't like them to be all there, apparently fighting at full strength, and suddenly *POP* they are gone! I want to glance at the table and be able to get an instant assessment of the strength of the forces on the field.
2 - I like to be able to play with the same models for different size games. Having them all on one big base means I can't really use them for skirmish games. Individual bases on (tasteful) movement trays means I can do both.
3 - I want to be able to go back to models and improve them, re-do parts at a later date. Having them all based together limits how much of this I can do. I also am constantly re-arranging how they are grouped into units, and at later dates will re-arrange them plenty more as more gets painted.
4 - Of course units look great based in groups, and it has the potential to have them look particularly realistic rather than lined up in perfect ranks. But looking at my models on their movement trays, lined up in 'perfect' ranks... Well, they look great like that too!
So I'm all for indivual 20mm square bases on movement trays. That's how I like it!
Something I am quite keen on is keeping the bases simple, but good. My basing technique is very easy - sand, not painted, just sealed with watered-down-PVA. Then with patches of one particular sort of static grass. That's it. Looks good. And it COMPLEMENTS the models, rather than distracting from them with colourful flowers and bushes and such.
However I do like my battles to look REALISTIC as best can be, and I don't like the idea of 10 models representing a huge regiment.... Obviously there has to be a compromise. So what I'm settling on is 'small battles', using my own ruleset which allows any unit to be in either open or close formation, and the latter works best when lots of units are linked up in a battleline. And when these ranked up groups are broken up and reduced to small numbers of men, the rules give them no bonuses for being ranked up and they are instantly 'un-ranked'. So rather than lots of random rectangles of 10 or 15 men spotted around the board, it's more likely to be one or two larger battleline groups, (consisting of several ranked up units), with smaller open formation units here and there.
I think these pics are a good example of what I've just described, and how I like it!

