Much depends on the condition of what you buy. Parts are getting scarce for even popular crawlers like Deere 350s. For a bigger 6 ton crawler (including blade) it's hard to beat an AC HD5 as a "farm dozer" that is built with easily found generic parts IF you can get along with a hand-clutch.
I needed a crawler small enough to trailer with my Ford F250 and got a Case 310G. 188 diesel, no steering clutches to worry about, 6 way blade, and all the undercarriage parts available. All gear drive, no steering clutches, a popular engine, etc. I recently bought new rollers for $80 each (from Korea of all places).
If you get serious about a Deere - especially a 350 - you'd better look VERY close. I come across many that are basically runing good but "beyond repair" in any cost-effective way. They tend to get loose where the trans case meets the reverser case and both cases and main shafts get ruined.
I was a Deere mechanic for many years, but my choice for an older crawler would favor a Case due to parts availability and simplicity. Or if bigger and newer - a CAT.
By the way, I've got a 1960 Deere 1010 crawler loader and love it. But - if the engine or the reverser ever lets go - I'd probably NOT fix it. Too pricey.