one has 10 valves more than the other :)

The 20v is faster.

HTH.

Firstly avoid the 2.0 whether in 10 or 20v guise. The 126 10v is woefully
underpowered, the 20v has enough but all the power is after 4500rpm and
making progress is hard work, tiring and not very good for mpg. Plus the
gearing is low and its noisy at cruising speed.

Over 70k in our previous 2.0 20v 850 (manual, saloon) it averaged 29mpg,
with a low of under 20 and never better than 33.

The 2.5 10v s70 which is now in the family (manual again) is a far better
and brisker beast despite still only having 144bhp. The engine is more like
a NA diesel, in that its got good low down torque and feels lazy, you can
leave it in 4th & 5th and trundle up hill and down dale pretty easily.
Oppositely to the 20valvers it pulls strongly from 2500rpm to 5000rpm then
runs out of puff. The gearing is slightly on the high side but that does
give very relaxed and serene cruising. An indicated 100 is only 3500rpm
which its happy at all day. Mpg is currently showing 31mpg consisting of
entirely 5-15mile trips to town with the occasional longer distance. I've
had nearly 40mpg on a long run at 60.

If you want an auto, or an estate which you will load, or regularly have a
full compliement of passengers you want at minimum the 20v 170. You will
find this heavier on fuel about town and about the same if not very slightly
better than the 10v on the motorway. The auto will drink more around town
and be equal cruising.

The best engine without doubt coupled to the auto box is the 193/200/210bhp
(depending on year) 2.5T. Fairly frugal for 200brake once you get used to
manipulating the accelorator to get the speed you want- they are deceptively
fast.

Hope this helps!

Tim..

10 valvers exist to reduce power for the euro markets that tax cars on power
output. They're fine for everyday use (140bhp  / 163 bhp IIRC for 10/20V 2.5
engines). Later ones (new shape V70, S80 etc)
went to just changing the ECU to reduce the max power to 140 and had 20v in
both outputs.

2.0 again really existed to keep certain markets happy, 2.0 20v isn't too
bad to drive, 2.0 Turbos are great. Bit better on fuel, but not much, than
the 2.5 / 2.4.