In the last few weeks, SPDR launched 10 foreign-sector ETFs, adding to the marketplace a third foreign-sector ETF methodology. WisdomTree weights components by dividends, and iShares is actually a mix of foreign and domestic stocks (what they call global). SPDR weights its foreign-sector ETFs by market capitalization.

No single methodology can be the best for all sectors all the time. If you want to build a portfolio sector by sector and include foreign-sector ETFs, you must take a close look at each sector and evaluate its health now and prospects down the road.

As an example, we can look at the health care sector:

iShares S&P Global Healthcare Sector Index Fund

WisdomTree International Healthcare Sector Fund

SPDR S&P International Healthcare Sector ETF

IXJ is actually quite heavy in the U.S., at 63%. Over the last couple of years it has lagged DBR because, broadly speaking, of its U.S. exposure -- and more narrowly because of its weighting in

Pfizer

(PFE) - Get Pfizer Inc. Report

, which currently stands at 5.6%.

Two years ago, Pfizer's market cap was close to $225 billion, vs. today's $125 billion -- so that roughly $100 billion of market cap lost has been a drag on IXJ.

Looking forward, I think Pfizer holds the key to whether IXJ will be the best choice in this space.

(Four years ago, I wrote an article that was bearish on Pfizer, because I did not see where it would find new revenue to provide strong growth. Estimates for this year call for $48 billion in revenue -- less than the revenue from four years ago.)

For now, I don't expect much from Pfizer, but at some point if there is a real resurgence, IXJ would clearly be the best hold. The bull case now for IXJ is the chance to own

Johnson & Johnson

(JNJ) - Get Johnson & Johnson (JNJ) Report

and

Novartis

TheStreet Recommends

(NVS) - Get Novartis AG Sponsored ADR Report

in one ETF.

DBR has some plusses (20% in Switzerland) and some minuses (23% in Japan). Switzerland is a plus, in my opinion, because the stocks tend to have lower volatility and the Swiss franc has been drifting higher against the dollar in the last couple of years. Japan is a negative as it doesn't seem the country can right itself from the last 18 years of decline. The largest Japanese stock in the fund,

Takeda Pharmaceuticals

(TKPHY)

, is down 30% since the market peaked last October.

The concern with Japan notwithstanding, DBR has outperformed IXJ by a meaningful amount.

IRY is too new to have any track record, but it is heavier in Switzerland (32%) and lighter in Japan (17%). IRY's two largest holdings are Novartis at 13.42% and Roche Holdings at 12.26% -- which is a lot of Switzerland, but the weight in Roche stands to get larger if it's successful in its bid to buy the remaining shares of

Genentech

(DNA)

it doesn't already own.

While I'm favorably disposed to Switzerland -- and Novartis especially -- IRY is clearly vulnerable to some sort of problem with these two stocks, or some crisis that might be unique to Switzerland.

Weighing the three leads me to think IRY would be the best choice going forward, but the main point is that you should do the work to look under the hood with any sector where an ETF is the best choice, to determine what is the best fit for you.

In other sectors, WisdomTree would be the best choice right now -- and in other sectors still, iShares would be the best choice now.

Looking further down the road, as mentioned, IXJ might become the best choice if things change for Pfizer -- and if Japan all of sudden were to provide meaningful leadership, I would think DBR would be the better choice.

At the time of publication, Nusbaum was long IXJ, DBR, JNJ and NVS on behalf of clients, although positions may change at any time.

Roger Nusbaum is a portfolio manager with Your Source Financial of Phoenix, and the author of Random Roger's Big Picture Blog. Under no circumstances does the information in this column represent a recommendation to buy or sell stocks. Nusbaum appreciates your feedback;

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