tl; dr—The spell clone is less expensive and can be employed on the PCs' behalf—ostensibly—without the DM's permission, but it's inconvenient and hard to find someone who can cast it; the spell resurrection is more expensive and incredibly convenient, yet it requires the DM's permission to see it cast on the party's behalf.
A quick overview of both spells
The 7th-level Clr spell resurrection [conj] (PH 272–3) takes 1 min. to cast and creates instantaneously—from whatever remains are left behind as long as there are any remains (even the dust left behind after a disintegrate effect is enough)—a body for dead creature if one isn't present and restores the creature to full health, ready to leap back into the action. If the DM allows such a service, a level 13 cleric can cast the spell resurrection at a price of 910 gp for the spell plus 10,000 gp for the material components.
The 8th-level Sor/Wiz spell clone [necro] (PH 210), after the spell's cast, mandates that the body created by the clone spell grow for 2d4 months in laboratory conditions, and, after that time, the soul of the dead creature can enter the body. Also, the dead creature's remains that are necessary for the spell must be either fresh or preserved like with the 3rd-level Sor/Wiz spell gentle repose [necro] (PH 235) or unguent of timelessness (DMG 268) (150 gp; 0 lbs.). If a high enough level caster can be found to cast of the clone spell, a level 16 sorcerer or a level 15 wizard can cast the clone spell at a price of 1,200 gp if cast by the wizard (the sorcerer charges an 80 gp more) plus 1,000 gp for the material components and 50 gp for the lab work (i.e. 10% of the cost of the spell's focus component).
(Note that in both cases, the fellow who's been brought back from the dead still loses a level or 2 points of Constitution! There are other subtle differences between the spells, of course, but I don't think they're important to this discussion. For example, I'm going to assume the creature being brought back from the dead was not turned into an undead creature and left by his colleagues to roam the countryside.)
A cleric typically won't sell a resurrection spell, but a sorcerer or wizard will typically sell a clone spell…
The Player's Handbook on Spellcasting and Services says, "If the additional costs [that include material components and 10% of a spell's focus components] put the spell's total cost above 3,000 gp, that spell is not generally available, except by the DM's permission" (129). This normally puts the price of the spell resurrection (10,910 gp) beyond reach except when it's cast by the PCs themselves. However, the price of spell clone (2,250 gp) makes the clone spell readily available even without the DM's permission… if a wizard or sorcerer can be found who can cast it!
…But finding a sorcerer or wizard who is able and willing to cast the clone spell is difficult
This reader doesn't know if your DM uses the Dungeon Master's Guide section on generating towns, but this DM does, and let me tell you, those high-level folks are rare.
Only a large city or bigger has the possibility of having a level 13 cleric or a level 15 wizard, and large cities and bigger only make up 5% of the towns in a Dungeon Master's Guide-generated world. Then, if a large or bigger city is discovered, there's a chance a cleric, sorcerer, or wizard of sufficient level to cast either spell resides in that town:
- In a large city, there are 3 high-level clerics; each of their levels is rolled randomly using 1d6+9. It's entirely possible that none of the clerics in that large city are high enough level to cast the spell resurrection even if the PCs are toting around diamonds worth 10,000 gp! Worse, the sorcerers and wizards in town are lower level than the clerics (their levels are determined by rolling 1d4+9), so there's no chance of a clone spell on hand there.
- In a metropolis—and there's a metropolis only on a roll of 100, by the way—, chances are better: there are 4 high-level clerics each of whom is level 1d6+12. There are also 4 high-level sorcerers and 4 high-level wizards, but each of them is only level 1d4+12. It's only if one of those sorcerers or wizards is, respectively, level 15 or higher or 16 that the clone spell becomes available.
(Finding high-level folks is easier if using the Epic Level Handbook rules for demographics (113–14), but this DM doesn't; I stop campaigns six or so sessions after PCs reach level 20. Things are already crazy enough by then.)
Finally, the Player's Handbook on Spellcasting and Services on Spells adds
Because you must get an actual spellcaster to cast a spell for you and can't rely on a neutral broker, money is not always sufficient to get a spell cast. If the spellcaster is opposed to you on religious, moral, or political grounds, you may not be able to get the spell you want for any price. The DM always sets the final price of any spellcasting you want to purchase. (132)
According to Table 4–7: Random NPC Alignment (DMG 110), NPCs are good only 20% of the time; 30% of the time they're neutral and 50% of the time they're evil. While this certainly won't be a factor in a campaign with a more nuanced view of alignment—or, of course, in one that dispenses with it—, in most campaigns being a different alignment from the caster—y'know, like, good—might put the prospective clients in religious, moral, or political opposition to the caster.