Two of the most popular ASX 200 tech stocks are Xero Ltd (ASX: XRO) and WiseTech Global Ltd (ASX: WTC).

And they are popular for good reason.

Not only do they have very strong business models and equally strong long-term growth outlook, they also consistently deliver the goods for investors.

For example, over the last 12 months, the Xero share price has risen 30%. Whereas for the WiseTech share price, it has climbed 32% over the same period.

This compares very favourably to the performance of the ASX 200 index, which is up almost 4% since this time last year.

Goldman Sachs has been running the rule over these ASX 200 tech stocks this week and has given its opinion on what the future could entail.

For now, though, the broker has a buy rating and $152.00 price target on Xero's shares and a neutral rating and $85.00 price target on WiseTech Global's shares.

But looking further ahead, the broker has provided investors with its blue-sky valuations for these ASX 200 tech stocks.

This is its "bull-case valuation analysis, to assess what current market pricing could potentially be factoring in across core and expansion TAMs."

For Xero, it sees scope for the company's shares to rise to $231.00. It explains:

Xero bull case of A$231 (+93% implied upside), ascribing A$118 to ANZ/UK, A$72 to the US and A$40 to its transaction businesses. Given historical challenges in the US, market pricing (A$120) could be implying a strong ANZ/UK performance, stable transaction revenues (i.e., 10.5% revenue), but potentially no value to the US, or improved transaction performance (i.e., greater pay attach). Given: (1) increased US focus within the 3×3; (2) improved product capability; (3) refreshed management team, we would view such pricing as overly cautious.

For WiseTech, it sees potential for this ASX 200 tech stock to climb to $126.00 if everything comes to plan. It adds:

WiseTech bull case of A$126 (+41% implied upside), ascribing A$59 to core, A$45 to Customs and A$22 to Landside/Warehousing. Given the strong early performance in Customs, (K&N and FedEx) but the weaker revenue outlook at Blume/Envase, market pricing (A$89) could be factoring in a high degree of success within the Core FF/Customs, but limited success in Landside.