Hi homiinbali,
Ok, there are a number of things one might consider.. Such as preferences, accessibility, investment returns, etc.. These different factors lead different people to choose different places all over the island.. So some areas that I considered and what and why we ended up goin with.
Ubud - people in ubud love the seclusion, the rich artistic culture, the stront nature elements, including often views over rice fields and the forest. Ubud can be expensive depending on where, be aware that most land advertised as ubud is around ubud, but not in actual ubud. Investment returns can be good here, some of the most expensive hotels in bali are here (amandari and there's another one more expensive).. And some villas that sell there are very high end.. Overall though, I found the market for selling here was more limited than say Jimbaran, legian, seminyak, kerobokan, and maybe even sanur.. Perhaps it's the proximity to the beach that ubud lacks, but it is beautiful..
Seminyak - already expensive, some views of rice fields available but prime is near the water.. Huge western population here and they seem to be very well integrated.. I.e. You see them all over the streets and riding around on motorbikes everywhere.. The area has a beautiful feel with many little stores and a strong cultural feel.. Definitely one of the more expensive areas, with tons of western villas.. The same goes for kerobokan, only kerobokan is a little less mature, so some cheaper land opportunities may exist..
Sanur - sanur is newer to me, we never really ventured to the east side of the island too often, went there once and thought it was great.. There are many villas there, some are older, and the areas a little further away from the central tourism mecca that is kuta, than say jimbaran..
The southern 'tear drop' - class 1 areas including jimbaran (and jimbaran as a location includes parts of ungasan), nusa dua and benoa.. These are my personal favourites - we bought and are building in jimbaran.. (remember all people have diff prefs) I'm very accustomed to this area as we always stay there.. There are big hotels there including the Conrad in benoa, the ritz in jimbaran (I think at bali cliffs) and the many many hotels in nusa dua (inc the sheraton laguna, just to name 1). These areas are largely in the hills, so many have views. There are tons of villas, the terrain is up and down, but very rocky (the soil) so no probs with sinking foundations as can be the problem in the rice field areas. Prized are the areas close to the beach with good access. High potential returns here if u pick your land wisely, but these areas attract a premium.. Expext to pay 75m to 125m per 100m2 inland and more on the coast, though it's very hard to come accross. Tons of westeners here with a nice cultural blend. Close proximity to all major tourist attractions..
The southern 'tear drop' - class 2 areas - including balangan, kampial and non jimbaran ungasan.. Some potential here, providing access is good.. These places will or should be cheaper than jimbaran, benoa and nusa dua.. My friend in bali swears by these places as great investment areas. They are the less westernized bukit areas, also on hills, often with great views.. Sometimes the access is a bit of an issue, but it will just be a matter of time.. U'll see a lot of this product on the market now..
Be careful on land around dreamland.. Most is under dispute.. Also, be very very aware of double certs existing in bali.. If the price seems too good to be true, it just might be..
The areas I've listed are just the ones I've investigated for purchase of land for primary residence and investment.. There are hundreds and hundreds of other locations u might with to consider like tanah lot, sigaraja (dunno how to spell it) and lovina beach (last 2 on the north of the island).. Each area offers something unique, and other members on the forum will be able to give u heaps of info on other places as well as maybe a different perspective on some places I've written about..
Hope this helps and good luck with ur search..
Ct..